Apple XSAN 2 Administrators Guide
Xsan 2
Administrator’s Guide
K
Apple Inc.
© 2008 Apple Inc. All rights reserved.
Under the copyright laws, this manual may not be
copied, in whole or in part, without the written consent
of Apple.
The Apple logo is a trademark of Apple Inc., registered
in the U.S. and other countries. Use of the “keyboard”
Apple logo (Option-Shift-K) for commercial purposes
without the prior written consent of Apple may
constitute trademark infringement and unfair
competition in violation of federal and state laws.
Every effort has been made to ensure that the
information in this manual is accurate. Apple is not
responsible for printing or clerical errors.
Apple
1 Infinite Loop
Cupertino, CA 95014-2084
408-996-1010
www.apple.com
Apple, the Apple logo, Mac, Mac OS, Macintosh, the Mac
logo, Tiger, Xsan, and Xserve are trademarks of Apple
Inc., registered in the U.S. and other countries.
Apple Remote Desktop, Finder, Leopard, and Spotlight,
are trademarks of Apple Inc.
ADIC and StorNext are registered trademarks of
Advanced Digital Information Corporation.
Intel, Intel Core, and Xeon are trademarks of Intel Corp.
in the U.S. and other countries.
PowerPC and the PowerPC logo are trademarks of
International Business Machines Corporation, used
under license therefrom.
UNIX is a registered trademark of The Open Group.
Other company and product names mentioned herein
are trademarks of their respective companies. Mention
of third-party products is for informational purposes
only and constitutes neither an endorsement nor a
recommendation. Apple assumes no responsibility with
regard to the performance or use of these products.
The product described in this manual incorporates
copyright protection technology that is protected by
method claims of certain U.S. patents and other
intellectual property rights owned by Macrovision
Corporation and other rights owners. Use of this
copyright protection technology must be authorized by
Macrovision Corporation and is intended for home and
other limited viewing uses only unless otherwise
authorized by Macrovision Corporation. Reverse
engineering or disassembly is prohibited.
Apparatus Claims of U.S. Patent Nos. 4,631,603, 4,577,216,
4,819,098 and 4,907,093 licensed for limited viewing
uses only.
Simultaneously published in the United States and
Canada.
019-0964-A/2008-01-16
1
Contents
Preface 9 About This Book
10
What’s New in Xsan 2
10
Version Compatibility
10
Upgrading from an Earlier Version of Xsan
11
Getting Additional Information
11
Notation Conventions
Chapter 1 13 Overview of Xsan
13
Xsan Storage Area Networks
14
15
15
15
16
16
17
17
18
19
19
19
19
20
20
21
Shared SAN Volumes
Metadata Controllers
Clients
Network Connections
How Xsan Storage Is Organized
LUNs
Storage Pools
Affinities
Volumes
Folders with Affinities
How Xsan Uses Available Storage
Metadata and Journal Data
Striping at a Higher Level
Security
Expanding Storage
Xsan Capacities
Chapter 2 23 Planning a Storage Area Network
23
Hardware and Software Requirements
23
24
24
25
26
Supported Computers
Supported Storage Devices
Fibre Channel Fabric
Ethernet TCP/IP Network
Directory Services
3
27
27
28
34
35
35
35
35
36
36
36
37
37
37
Outgoing Mail Service
Planning Your SAN
Planning Considerations and Guidelines
Planning the Ethernet TCP/IP Network
Using a Private Metadata Network
Using Switches Instead of Hubs
Planning the Fibre Channel Network
Verifying Base Fibre Channel Performance
If Your Fibre Channel Fabric Is Running Slower Than Expected
Configuring RAID Systems
Installing the Latest Firmware
Connecting RAID Systems to an Ethernet Network
Choosing RAID Levels for LUNs
Adjusting RAID System Performance Settings
Chapter 3 39 Setting Up a Storage Area Network
39
Connecting Computers and Storage Devices
39
Preparing LUNs
40
Using Server Assistant to Configure Controllers
40
40
40
41
41
41
41
41
41
42
51
51
52
52
52
Managing Users and Groups with Xsan Admin
Using an Existing Open Directory Server
Using Another Directory Server
Using Xsan Admin
Installing Just the Xsan Admin Application
Connecting Through a Firewall
Xsan Admin Preferences
Getting Help
SAN and Volume Setup Summary
Setting Up an Xsan Volume on a Storage Area Network
Setting Up an Xsan Administrator Computer
Renaming a SAN
Removing a SAN
Managing Multiple SANs
Setting Up Additional SANs
Chapter 4 53 Managing SAN Storage
53
Adding Storage
54
54
55
56
57
58
4
Preparing LUNs
Finding the Drive Modules That Belong to a LUN
Adding LUNs to a Storage Pool
Rearranging Fibre Channel Connections
Adding a Storage Pool to a Volume
Adding a Volume to a SAN
Contents
59
Setting Up a Folder Affinity
60
Changing a Folder’s Storage Pool Affinity
60
Removing an Affinity
61
Changing Advanced Volume Settings
62
63
63
63
64
64
65
65
65
66
67
67
68
68
69
Setting the Block Allocation Size
Changing the Volume Allocation Strategy
Enabling or Disabling Spotlight on a Volume
Enabling or Disabling Access Control Lists
Changing the Windows ID Mapping
Changing Advanced Allocation and Cache Settings
Renaming a Volume
Changing Storage Pool Settings
Choosing the Data Type for an Affinity Tag
Setting the Storage Pool Stripe Breadth
Checking Volume Fragmentation
Defragmenting a Volume
Checking the Integrity of a Volume
Repairing a Volume
Destroying a Volume
Chapter 5 71 Managing Clients and Users
72
Adding a Client
73
Adding an Xsan Serial Number
74
Moving a Client to a Different SAN
75
Mounting a Volume on a Client
76
77
78
79
79
79
80
80
80
80
81
82
83
84
85
86
87
89
Changing Mount Options
Managing Users and Groups
Adding SAN Users
Deleting SAN Users
Creating Groups
Deleting Groups
Changing Group Membership
Controlling Client and User Access
Controlling File and Folder Access Using the Finder
Controlling File and Folder Access Using Xsan Admin
Unmounting a Volume on a Client
Restricting a Client to Read-Only Access
Removing a Client from a SAN
Mapping Windows User and Group IDs
Setting SAN User and Group Quotas
About Xsan Quotas
Checking User Quota Status
Helping Clients Check Their Own Quotas
Contents
5
89 Creating Local Home Folders for Network Accounts
90 Accessing Client Computers Remotely
90 Controlling a Client Using Screen Sharing
91 Connecting to a Client Using SSH in Terminal
91 Managing a Client Server Using Server Admin
Chapter 6 93 Managing Metadata Controllers
94 Adding a Metadata Controller
95 Setting Controller Failover Priority
95 Switching to a Standby Controller
96 Finding Out Which Controller Is Hosting a Volume
97 Listing the Volumes Hosted by a Controller
97 Changing a Controller’s IP Address
98 Accessing Controller Computers Remotely
98 Controlling a Controller Using Screen Sharing
99 Connecting to a Controller Using SSH in Terminal
99 Managing a Controller Using Server Admin
99 Monitoring Controller Status
Chapter 7 101 Monitoring SAN Status
101 Checking SAN Status
10 2 Checking Volume Status
10 3 Checking Free Space on a Volume
10 4 Checking Free Space on a Storage Pool
10 4 Graphing SAN Resource Usage
10 5 Setting Up Status Notifications
10 6 Viewing Xsan Logs
10 7 Checking Volume Clients
10 8 Checking for Fibre Channel Connection Failures
Chapter 8 109 Solving SAN Problems
10 9 If You’re Unable to Connect to a Computer Using Xsan Admin
10 9 If You’re Unable to Install the Xsan Software
10 9 If Some Computers Aren’t Listed in Xsan Admin
11 0 If You’re Unable to Mount a Volume on a Client
11 0 If RAID LUNs Aren’t Accessible over Fibre Channel
11 0 If Files and Folders Created by Mac OS 9 Computers Show the Wrong Creation Date
11 0 If You Have Problems Using Command-Line Tools
11 0 If a LUN Doesn’t Have as Much Space as Expected
11 0 If You’re Unable to Rename an Xsan Volume in the Finder
111 If You’re Unable to Add a Storage Pool
111 If Fibre Channel Performance Is Poorer Than Expected
112 If a Client is Unable to Use a Volume After a Fibre Channel Interruption
6
Contents
112 If You’re Unable to Add LUNs to a Storage Pool
113 If the Capacity of a Larger LUN is Listed as 2 Terabytes
113 If File Copying Doesn’t Finish
Appendix A 115 Combining Xsan Controllers and StorNext Clients
11 5 Terminology
11 6 Compatible Software Versions
11 6 Licensing
117 Using Xsan Controllers with StorNext Clients
Appendix B 119 Using the Command Line
11 9 Using the Shell Commands
11 9 Sending Commands to Remote Computers
12 0 Viewing the Man Pages
12 0 Notation Conventions
12 0 Installing Xsan from the Command Line
121 Xsan Commands
121 Viewing or Changing Volume and Storage Pool Settings (cvadmin)
12 4 Manipulating Affinity Tags (cvaffinity)
12 4 Copying Files or Folders (cvcp)
12 5 Checking or Repairing a Volume (cvfsck)
12 6 Labeling, Listing, and Unlabeling LUNs (cvlabel)
12 7 Creating a Folder and Assigning an Affinity (cvmkdir)
12 7 Creating and Preallocating a File (cvmkfile)
12 8 Initializing a Volume (cvmkfs)
12 8 Applying Volume Configuration Changes (cvupdatefs)
12 8 Defragmenting a File, Folder, or Volume (snfsdefrag)
13 0 Controlling the Xsan File System (xsanctl)
13 0 Mounting an Xsan Volume
13 0 Unmounting an Xsan Volume
131 Viewing Logs
131 Xsan Configuration Files
131 Examples
Glossary 13 3
Index 13 7
Contents 7
8 Contents
About This Book
Use this guide to learn how to use Xsan 2 set up and manage
volumes on a storage area network.
This guide shows how to use Xsan 2 to combine RAID arrays into large, easy-to-expand
volumes of storage that clients use like local disks but are actually shared over a highspeed Fibre Channel fabric.
Chapter 1 provides an overview of Xsan and how you can use it to organize RAID arrays
into shared volumes of storage.
Chapter 2 describes hardware and software requirements, and offers SAN planning
guidelines.
Chapter 3 shows the basic steps for setting up a SAN.
Preface
Chapter 4 contains instructions for expanding storage, creating folders with affinities,
changing volume and storage pool settings, and checking, defragmenting, and
repairing SAN volumes.
Chapter 5 shows how to add client computers to a SAN, mount volumes on clients,
control client and user access to SAN files, and control user space through quotas.
Chapter 6 contains information about managing volume metadata controllers.
Chapter 7 shows how to monitor and automatically report the condition of a SAN.
Chapter 8 lists solutions to common problems you might encounter.
Appendix A contains information to help you combine Xsan metadata controllers with
Quantum StorNext clients on the same SAN.
Appendix B describes command-line utilities and configuration files you can use to
manage an Xsan SAN using the Terminal application.
9
What’s New in Xsan 2
Xsan 2 offers these new features and capabilities:
 The Xsan Admin application has been redesigned to simplify SAN management.
 You can use Xsan Admin to turn on drive activity lights to identify LUNs.
 A volume setup assistant guides you through the process of creating volumes for
common purposes such as video editing and file services.
 The volume setup assistant also organizes available storage into storage pools for
you, based on the way you plan to use the volume.
 More than one storage pool can have the same affinity tag.
 Each volume has a separate failover priority.
Version Compatibility
The following table shows the compatibility of Xsan 2 metadata controllers and clients
with earlier Xsan versions and with StorNext controllers and clients.
Controller Client Compatible
Xsan 2 Xsan 2 (Mac OS X v10.5) Yes
Xsan 1.4.2 (Mac OS X V10.4 or
v10.5)
Xsan 1.4–1.4.1 No
Xsan 1.3 or earlier No
StorNext FX 1.4 or 2.0 Yes
StorNext FS 2.4–3.1 No
Xsan 1.4 or earlier Xsan 2 No
StorNext FS 3.1 Xsan 2 Yes
StorNext FS 2.4–3.0 Xsan 2 No
Yes
Upgrading from an Earlier Version of Xsan
For information about upgrading your SAN storage to Xsan 2 from an earlier version of
Xsan, including precautions to take before upgrading and tips for upgrading with the
least impact on existing storage, see the Xsan 2 Migration Guide at www.apple.com/
server/documentation.
10 Preface About This Book
Getting Additional Information
For more information about Xsan, consult these resources:
Read Me documents (on the Xsan Install Disc)
Read important updates and special information
Server documentation website (www.apple.com/server/documentation)
Get the latest Xsan documentation available in PDF format
Xsan website (www.apple.com/xsan)
Visit the gateway to extensive product and technology information
Xsan Support website (www.apple.com/support/xsan)
Find articles about Xsan from Apple’s support organization
Apple Discussions website (discussions.apple.com)
Join a discussion group to share questions, knowledge, and advice with other Xsan administrators
Apple Mailing Lists website (www.lists.apple.com)
Subscribe to mailing lists so you can communicate with other Xsan administrators using email
Notation Conventions
The following conventions are used in this book wherever shell commands or other
command-line items are described.
Notation Indicates
fixed-width font A command or other text typed in a Terminal window
$ A shell prompt
[text_in_brackets] An optional parameter
(one|other) Alternative parameters (type one or the other)
italicized
[...] A parameter that may be repeated
<angle_brackets> A displayed value that depends on your SAN configuration
A parameter you must replace with a value
Preface About This Book 11
12 Preface About This Book
1 Overview of Xsan
1
This chapter gives you an overview of Xsan and storage area
networks.
Read this chapter for an overview of Xsan and how you can use it to set up a storage
area network (SAN) to provide fast, shared storage.
Mac OS X
San Volume
Storage
pools
Xsan lets you
combine RAID arrays
into volumes clients
use like local disks.
RAID
arrays (LUNs)
File data moves
over Fibre Channel
Xsan Storage Area Networks
A storage area network is a way of connecting computers and storage devices so that
the computers have fast, shared access to files while making it easy for administrators
to expand storage capacity.
13
An Xsan SAN consists of:
 Shared data volumes
 RAID systems that provide storage space that is protected against disk failure
 At least one computer acting as a metadata controller that combines the RAID arrays
and presents their storage to clients as one or more volumes that behave like local
disks
 Client computers that access storage in accordance with established permissions and
quotas
 Underlying Fibre Channel and Ethernet networks
The following illustration shows the hardware components of an Xsan SAN.
Standby
controller
Intranet/
Internet
Ethernet (public)
Ethernet (private)
RAID arrays
(LUNs)
Clients
Ethernet switches
Metadata
controller
Fibre
Channel switch
Metadata RAID array
(LUN)
Shared SAN Volumes
A user or application on a client computer accesses shared SAN storage just like they
would a local volume. Xsan volumes are logical disks made up of pools of RAID arrays.
The elements you combine to create an Xsan volume are described under “How Xsan
Storage Is Organized” on page 16.
14 Chapter 1 Overview of Xsan
Metadata Controllers
When you set up an Xsan SAN, you assign at least one computer to act as the metadata
controller. The controller manages volume metadata, maintains a file system journal,
and controls concurrent access to files. Metadata includes such information as where
files are actually stored and what portions of available storage are allocated to new
files.
To guarantee volume availability, a SAN should include more than one metadata
controller, as shown in the illustration on page 14. If the primary controller fails, the
standby controller takes over. Though not recommended for best performance,
metadata controllers can also act as clients, so you can use a standby controller as a
working client while the primary controller is operational.
Clients
The computers that users or applications use to access SAN volumes are called clients.
Clients exchange metadata with controllers over the Ethernet network but use Fibre
Channel to send and retrieve file data to and from the RAID systems that provide
storage for the volumes.
Network Connections
Xsan uses independent networks to connect storage devices, metadata controllers, and
client computers: a Fibre Channel network and one or two Ethernet networks.
Fibre Channel
Xsan moves data between clients and SAN volumes over high-speed Fibre Channel
connections. Controllers also use a Fibre Channel connection to move metadata to and
from the volume.
Xsan can take advantage of multiple Fibre Channel connections between clients and
storage. Xsan can alternate between connections for each read and write, or assign
each RAID array in a volume to one of the connections when the volume is mounted.
Ethernet
To prevent metadata traffic from interfering with data on the Fibre Channel network,
Xsan controllers and clients exchange file system metadata over a separate Ethernet
network. (Controllers do use Fibre Channel to read and write metadata on a volume.)
The Xsan Admin application also uses this Ethernet network to let you manage the
SAN.
To prevent Internet or intranet traffic from interfering with metadata communications,
you should set up separate public (Internet) and private (metadata) Ethernet networks
as shown in the illustration on page 14.
Chapter 1 Overview of Xsan 15
How Xsan Storage Is Organized
Although an Xsan volume mounted on a client computer looks like a single disk, it
actually consists of multiple physical disks combined on several levels using RAID
techniques.
The following illustration shows an example of how disk space provided by the
individual drive modules in several RAID systems is combined into a volume that users
see as a large local disk.
adata
et
M
and journal
Video
Video Other
Audio
Video
Audio
Other
RAID 0RAID 5RAID 5RAID 5RAID 5RAID 5RAID 5RAID 1
SAN volume
Folder affinities
Affinity tags
Storage pools
Data striping
across LUNs
RAID arrays
(LUNs)
The following paragraphs describe these elements and how you combine them to
create shared Xsan volumes.
LUNs
The smallest storage element you work with in Xsan is a logical storage device called a
LUN (a SCSI logical unit number). A LUN represents a group of drives combined into a
RAID array.
You create a LUN whenever you create a RAID array on a RAID storage device. The RAID
system combines individual drive modules into an array based on the RAID scheme
you choose. Each array appears on the Fiber Channel network as a LUN.
Most RAID systems ship already configured as RAID arrays. The corresponding LUNs are
ready to use with Xsan.
16 Chapter 1 Overview of Xsan
If the standard RAID arrays on your RAID systems are not right for your application, you
can use the RAID system management software to recreate arrays based on other RAID
schemes or different numbers of drive modules. For information about other RAID
schemes, see “Choosing RAID Schemes for LUNs” on page 30.
The illustration on page 16 shows eight RAID array LUNs. The LUN that stores metadata
and journal information uses RAID level 1 (mirrored) to ensure against metadata loss.
One LUN stores users’ data on a RAID 0 array (striping only) for best speed and storage
efficiency but no data protection. The other data LUNs use RAID 5 (distributed parity)
for high performance and storage efficiency with data protection. Xsan sees the RAID
arrays as LUNs that can be combined to create a volume.
Your RAID LUNs are labeled and initialized for use with the Xsan file system when you
use Xsan Admin to set up a volume.
Storage Pools
LUNs are combined to form storage pools. A storage pool in a small volume might
consist of a single RAID array, but a larger volume might consist of several storage
pools each of which includes several arrays.
Xsan distributes file data in parallel across the LUNs in a storage pool using a RAID 0
(striping) scheme. So, you can improve a client’s access speed by distributing available
storage over several LUNs in a storage pool.
You can set up storage pools that have different performance or recoverability
characteristics based on the RAID level of their LUNs, and assign folders to them using
affinities. Users can then select where to store files based on their need for speed or
safety. See “Folders with Affinities” on page 19.
The illustration on page 16 shows seven LUNs combined into four storage pools for
users’ data. One pool uses a single RAID 0 array (fast, but not recoverable). Three other
pools use multiple RAID 5 arrays (not as fast, but recoverable), and Xsan stripes data
across the LUNs in each of these storage pools.
You use Xsan Admin to add available LUNs to storage pools.
Affinities
Each storage pool is assigned an affinity tag according to the pool’s performance and
recoverability characteristics. You can associate a folder with an affinity tag to
guarantee that Xsan stores the contents of the folder on a storage pool with the
desired characteristics.
Chapter 1 Overview of Xsan 17
More than one storage pool may have the same affinity tag. Xsan distributes the
contents of a folder with a particular affinity tag among the storage pools that have
that same affinity tag. This strategy improves performance when multiple users
simultaneously read and write files in the same folder, because the read and write
operations are distributed among the storage pools and their component LUNs.
You use Xsan Admin to assign affinity tags to storage pools and associate folders with
those affinity tags.
Volumes
Storage pools are combined to create the volumes that users see. From the user’s
perspective, the SAN volume looks and behaves just like a large local disk, except that:
 The size of the volume can grow as you add underlying arrays or new storage pools
 Multiple users on the SAN can access files on the volume at the same time
In the illustration on page 16, five storage pools are combined to create a single shared
volume. You use Xsan Admin to create volumes and mount them on client computers.
The following screen shot shows how LUNs, storage pools, and volumes look as you
organize them in Xsan Admin. This example shows a SAN with a single shared volume
named “SanVol.” Storage for the volume is provided by three storage pools, “Meta,”
“Data1,” and “Data2,” the first based on a single LUN and the others on two LUNs each.
18 Chapter 1 Overview of Xsan
Volume
Storage
pool
LUN
Folders with Affinities
To control which storage pools are used to store specific files (for example, to provide
different levels of service for different users or applications), you can associate a folder
on an Xsan volume with an affinity that is assigned to one or more of the storage pools
that make up the volume.
For example, you can associate some folders with an affinity whose storage pools have
faster LUNs, and associate other folders with an affinity whose storage pools have safer
LUNs. Then users can choose between faster and safer storage by putting files in the
appropriate folder.
In the illustration on page 16, the Other folder has an affinity for the faster storage pool
that is based on a RAID 0 array. Any file that a user copies into the Other folder is
automatically stored on the faster array. The Video and Audio folders are associated
with the more secure RAID 5 storage.
How Xsan Uses Available Storage
Xsan stores both user files and file system data on SAN volumes, and stripes data across
the LUNs in a volume for better performance.
Metadata and Journal Data
Xsan records information about the files in an Xsan volume using metadata files and
file system journals. File system metadata includes information such as which specific
parts of which disks are used to store a particular file and whether the file is being
accessed. The journal data includes a record of file system transactions that can help
ensure the integrity of files in the event of a failure.
These files are managed by the Xsan metadata controller, but are stored on SAN
volumes, not on the controller itself. By default, metadata and journal data are stored
on the first storage pool you add to a volume. You can use Xsan Admin to choose
where these files are stored when you add storage pools to a new volume.
Striping at a Higher Level
When a RAID system writes a file using a RAID 0 (striping) scheme, it breaks the file into
segments and spreads them across the individual disk drives in the RAID array. This
improves performance by writing parts of the file in parallel (instead of one part at a
time) to the individual disks in the array. Xsan applies this same technique at a second,
higher level in the storage hierarchy. Within each storage pool in a volume, Xsan stripes
file data across the individual LUNs that make up the storage pool. Once again,
performance is improved because data is written in parallel.
You can tune SAN performance by adjusting the amount of data written to each LUN in
a storage pool (the “stripe breadth”) to suit a critical application.
Chapter 1 Overview of Xsan 19
Security
There are several ways you can control access to a SAN volume:
 Unmount a volume on client computers that shouldn’t have access to it. Users
cannot browse or mount SAN volumes; only a SAN administrator can mount SAN
volumes on clients.
 Mount a volume on a client for read-only access to prevent users on a particular
client computer from modifying data on the volume.
 Specify owner, group, and general access permissions in Xsan Admin.
 Specify owner, group, and general access permissions in the Finder.
 Control user access to files and folders on a volume by setting up access control lists
(ACLs) in Xsan Admin.
 Set up zones in the underlying Fibre Channel network to segregate users and
volumes.
Expanding Storage
There are two ways you can add free space to an existing Xsan volume:
 Add RAID systems (new LUNs) to existing storage pools
 Add entire new storage pools to the volume
Both methods automatically unmount and remount the volume on clients.
You can also add new volumes to a SAN at any time.
For information about expanding Xsan storage, see “Adding Storage” on page 53.
20 Chapter 1 Overview of Xsan
Xsan Capacities
The following table lists limits and capacities for Xsan volumes.
Parameter Maximum
Number of computers on a SAN (metadata controllers and clients) 64
Number of volumes on a SAN 16
Number of storage pools in a volume 512
Number of LUNs in a storage pool 32
Number of LUNs in a volume 512
Number of files in a volume 4,294,967,296
LUN size Limited only by the size of the
RAID array
Volume size Limited only by the number and
size of LUNs
File size Approximately 2
Volume name length 70 characters (A–Z, a–z, 0–9,
and _ )
File or folder name length 251 ASCII characters
SAN name length 255 Unicode characters
Storage pool name length 255 ASCII characters
Affinity name length 8 ASCII characters
LUN name (label or disk name) 242 ASCII characters
63
bytes
Chapter 1 Overview of Xsan 21
22 Chapter 1 Overview of Xsan
2 Planning a Storage Area Network
2
This chapter lists Xsan hardware and software requirements
and offers planning guidelines and performance tips that can
help you design a SAN that meets your needs.
This chapter contains:
 Xsan hardware and software requirements (page 23)
 SAN planning guidelines (page 27)
Hardware and Software Requirements
Your SAN environment needs to satisfy requirements in these areas:
 Supported computers
 Supported storage devices
 Fibre Channel fabric, adapters, and switches
 Ethernet network
 Directory services (optional)
 Outgoing mail service (optional)
Supported Computers
You can use Xsan 2 on computers that meet these minimum requirements:
Base Systems
 Macintosh computers with an Intel or PowerPC G5 processor
Memory
 Client computers need at least 2 GB of RAM (clients with Xsan 1.4.2 and Mac OS X
v10.4 Tiger or Mac OS X Server v10.4 Tiger need at least at least 1 GB).
 Computers used as metadata controllers need at least 2 GB of RAM for a single
volume plus an additional 2 GB of RAM for each additional SAN volume hosted by
the controller.
23
Supported Operating Systems
You can install Xsan 2 only on computers with Mac OS X v10.5 Leopard or Mac OS X
Server v10.5 Leopard.
Mac client computers that have Xsan 1.4.2 can join an Xsan 2 SAN. These clients can
have Leopard or Tiger.
To join an Xsan 2 SAN, Windows, AIX, IRIX, Linux, and Solaris clients must be running
Quantum’s StorNext File System version 2.6 or 2.7. For complete compatibility
information, see “Version Compatibility” on page 10.
Supported Storage Devices
Although you can use any standard SCSI LUN storage device, this guide assumes you
are using Apple-approved RAID systems for your storage devices. For the latest
information about qualified RAID systems, see the Xsan webpage at:
www.apple.com/xsan
Important: Be sure to install the latest firmware update on your RAID systems before
you use them with Xsan.
Fibre Channel Fabric
Unlike file system metadata, which controllers and clients exchange over Ethernet,
actual file content in an Xsan SAN is transferred over Fibre Channel connections (as is
metadata that controllers access on a volume). To set up the connections, you need:
 An Apple Fibre Channel PCI, PCI-X, or PCI-E card for each client and controller
computer
 A supported Fibre Channel switch
 Fibre Channel cables connecting computers and storage devices to the switches to
form a Fibre Channel fabric
Fibre Channel PCI Cards
Install Apple Fibre Channel PCI, PCI-X, or PCI-E cards in all Macintosh computers that
will connect to the SAN.
Fibre Channel Switches
Fibre Channel switches from Brocade, Cisco, and QLogic have been tested with Xsan
and the Apple Fibre Channel PCI, PCI-X, and PCI-E cards. For the latest information
about qualified switches, see the Xsan webpage at:
www.apple.com/xsan
24 Chapter 2 Planning a Storage Area Network
Fabric Configuration
You must connect the computers, storage devices, and switches in your Fibre Channel
network to form a Fibre Channel “fabric.” All Apple-approved switches create a fabric by
default as soon as you plug in the Fibre Channel cables. In a fabric, Fibre Channel
cables connect node ports (F or N_Port). See the documentation that came with your
Fibre Channel switches for more information.
Ethernet TCP/IP Network
Computers on the SAN must also be connected to an Ethernet network. Xsan
controllers and clients use this network instead of the Fibre Channel network to
exchange file system metadata.
If the computers on your SAN need to communicate with directory servers, a corporate
or campus intranet, or the Internet, you should connect each SAN client and metadata
controller to two separate Ethernet networks: one private subnet for the SAN metadata
and a separate connection for directory service, intranet, and Internet traffic. This is
especially important if you plan to use the SAN for high-performance applications such
as video editing.
IP Addresses
The client and metadata controller computers need static (fixed) IP addresses for their
Ethernet network connections. For the public intranet and Internet connection, you can
enter each computer’s static IP address, subnet mask, router address, and DNS server
address manually or configure a DHCP server to provide some or all of this information.
If you want the DHCP server to provide IP addresses, it must always assign the same
static IP address to each SAN computer. Don’t use DHCP to assign dynamic IP addresses
to SAN devices.
For the SAN metadata network, the SAN computers should have static private (nonroutable) IP addresses (unless you’re unable to set up a separate, private Ethernet
network for SAN metadata). If you’re setting up new computers or computers on which
you have just performed a clean installation of Leopard or Leopard Server, you can
have Xsan Admin assign and manage addresses for your private metadata network. If
you choose to assign addresses yourself, you can use one of the following ranges of IP
addresses on your private (non-routed) metadata network:
Private address range Associated subnet mask Comments
10.0.0.0 – 10.255.255.255 255.0.0.0 10/8
172.16.0.0 – 172.31.255.255 255.240.0.0 172.16/12
192.168.0.0 – 192.168.255.255 255.255.0.0 192.168/16
Chapter 2 Planning a Storage Area Network 25
Directory Services
If you plan to use user and group privileges to control access to files and folders on the
SAN, you should set up or join a central directory of users and groups. A central
directory service lets you manage all SAN users and groups from one computer instead
of having to visit and painstakingly configure each SAN client and metadata controller.
If you already have directory service provided by an Open Directory server, you can
have the setup assistant configure each metadata controller and client computer with
Xsan 2 to use existing user and group accounts from the Open Directory server. If you
have another type of directory service, such as Active Directory, you configure each
controller and client to connect to it for user and group accounts by using the
Directory Utility application after initial setup. If you have client computers with Tiger,
you use the Directory Access application on each one to connect it to a directory
server.
If your SAN doesn’t have access to an existing directory service, you can specify during
initial setup of your Xsan primary metadata controller that you want to use Xsan Admin
to manage your users and groups. The setup assistant creates an Open Directory
master server on your primary metadata controller and sets up Open Directory replica
servers on your standby metadata controllers. The Open Directory master provides an
LDAP directory, single sign-on user authentication using Kerberos, and password
validation using common authentication methods. The replicas improve responsiveness
and provide automatic failover of Open Directory services.
The setup assistant also configures client computers that have Xsan 2 installed to
connect to your Xsan primary metadata controller for Open Directory user and group
accounts. If you have client computers with Tiger, you need to use the Directory Access
application on each one to connect it to your Xsan primary metadata controller’s Open
Directory service.
If you need to set up an Open Directory server yourself, you can use Mac OS X Server’s
Server Admin application. Then you use the Workgroup Manager application to
manage users and groups. For information, see Open Directory Administration and User
Management at www.apple.com/server/documentation.
Note: Some applications running on SAN client computers, such as Final Cut Pro, work
better when users have local home folders, not network home folders. User accounts
that you manage with Xsan Admin are automatically set up with local home folders.
For help setting up local home folders for user accounts that you don’t manage with
Xsan Admin, see “Creating Local Home Folders for Network Accounts” on page 89.
If you decide not to use a central directory service, you need to set up the same users
and groups in the Accounts pane of System Preferences on each SAN computer.
26 Chapter 2 Planning a Storage Area Network
Important: If you create users and groups on each SAN computer, be sure that:
 Each user or group has a numeric user ID (UID) or group ID (GID) that is unique
throughout the SAN
 Each user or group defined on more than one computer has the same UID or GID on
each computer
Outgoing Mail Service
Xsan can send SAN status notifications via email on your local network (IP subnet)
without using a separate mail server. However, to send notifications outside your local
network, you need an SMTP server to act as a mail gateway. If you don’t have access to
an outgoing mail server, you can use the mail service in Mac OS X Server to set one up.
For information, see Mail Service Administration at www.apple.com/server/
documentation.
Planning Your SAN
It’s easy to add storage to an existing Xsan SAN, but reorganizing a SAN after you set it
up is not so simple. So, it’s important to plan the layout and organization of your SAN
and its storage before you set it up.
An Xsan SAN is made up of:
 Storage devices (RAID systems)
 LUNs (SCSI logical unit numbers, usually RAID arrays)
 Storage pools (groups of LUNs)
 Affinity tags, which identify storage pools with similar performance and data
protection
 Volumes (groups of storage pools visible to users)
 Clients (computers that use volumes)
 Controllers (computers that manage volume metadata)
 An Ethernet network used to exchange volume metadata
 A Fibre Channel network used to transfer data to and from volumes
Before you try to set up a SAN, you need to decide how you want to organize these
components. Take the time to create a diagram or a table that organizes available
hardware into RAID arrays, volumes, client computers, and metadata controllers in a
way that meets SAN users’ needs and your needs as the SAN administrator. You don’t
need to plan your storage pools or affinity tags if you set up each volume using a
preset volume type based on the kind of work the volume will support.
Preliminary Planning Questions
As you plan, consider the following questions:
 How much storage do you need?
Chapter 2 Planning a Storage Area Network 27
 How do you want to present available storage to users?
 What storage organization makes the most sense for user workflow?
 What levels of performance do your users require?
 How important is high availability?
 What are your requirements for security?
Your answers to the above questions will help you decide the following:
 What RAID schemes should you use for your RAID arrays?
 How many SAN volumes do you need?
 How should individual volumes be organized?
 Which preset volume type can you choose for each volume?
 Which LUNs should be assigned to each affinity tag?
 Which clients, users, and groups should have access to each volume?
 Which computers will act as metadata controllers?
 Do you need standby metadata controllers?
 Do you want to use metadata controllers as clients also?
 Do you need to customize the storage location of file system metadata and journal
data?
 Do you need to adjust a volume’s allocation strategy?
 How should you configure your Ethernet network?
Review the considerations and guidelines on the following pages for help translating
your answers into a suitable SAN design.
Planning Considerations and Guidelines
The following paragraphs might help you make some of your SAN design decisions.
How Much Storage?
Because it’s easy to add storage for user data to an Xsan SAN, you only need to decide
on an adequate starting point. You can add storage later as needed.
However, you can’t expand a storage pool that can only store volume metadata and
journal data, so you should try to allocate enough space for metadata right from the
start. (You can add an entire storage pool for metadata and journal storage.) For help
estimating your metadata and journal data storage requirements, see “Estimating
Metadata and Journal Data Storage Needs” on page 34.
Note that the number of RAID systems you use affects not only available space but also
SAN performance. See “Performance Considerations,” below.
28 Chapter 2 Planning a Storage Area Network
How Should Users See Available Storage?
If you want the users working on a particular project to see a volume dedicated to their
work, create a separate volume for each project. If it’s acceptable for a user to see a
folder for his or her work on a volume with other peoples’ folders, you can create a
single volume and organize it into project folders.
Workflow Considerations
How much file sharing is required by your users’ workflow? If, for example, different
users or groups work on the same files, either simultaneously or in sequence, it makes
sense to store those files on a single volume to avoid having to maintain or hand off
copies. Xsan uses file locking to manage shared access to a single copy of the files.
Performance Considerations
If your SAN supports an application (such as high resolution video capture and
playback) that requires the fastest possible sustained data transfers, design your SAN
with these performance considerations in mind:
 Set up the LUNs (RAID arrays) using a RAID scheme that offers high performance. See
“Choosing RAID Schemes for LUNs” on page 30.
 Assign your fastest LUNs to an affinity tag for the application. Assign slower LUNs to
an affinity tag for less demanding applications.
 To increase parallelism, spread LUNs across different RAID controllers. Xsan then
stripes data across the LUNs and benefits from simultaneous transfers through two
RAID controllers.
 To increase parallelism for an affinity tag assigned to relatively small LUNs (the size of
one or a few drive modules), create a slice of similar size across all the drives on a
RAID controller instead of creating the LUNs from just one or two drive modules.
 Spread file transfers across as many drives and RAID controllers as possible.
Try creating slices across the drives in RAID systems, and then assign these slices to
the same affinity tag.
 To increase throughput, connect both ports on client Fibre Channel cards to the
fabric.
 Store file system metadata and journal data on a separate storage pool from user
data, and make sure the metadata LUNs are not on the same RAID controller as any
user data LUNs.
 Use a second Ethernet network (including a second Ethernet port in each SAN
computer) for the SAN metadata, or at least use a router to isolate the Ethernet
network used by the SAN from a company intranet or the Internet.
 If your SAN uses directory services, mail services, or other services on a separate
server, connect SAN computers to that server on an Ethernet network separate from
the SAN metadata network.
Chapter 2 Planning a Storage Area Network 29
 Choose a different primary metadata controller for each volume, and set up volume
failover priorities to minimize the possibility of more than one volume failing over to
the same metadata controller.
Availability Considerations
If high availability is important for your data, set up at least one standby metadata
controller in addition to your primary metadata controller. Also, consider setting up
dual Fibre Channel connections between each client, metadata controller, and storage
device using redundant Fibre Channel switches.
WARNING: Losing a metadata controller without a standby can result in the loss of all
data on a volume. A standby controller is recommended.
Security Considerations
If your SAN will support projects that need to be completely secure and isolated from
each other, you can create separate volumes for each project to eliminate any
possibility of the wrong client or user accessing files stored on a volume.
As the SAN administrator, you control which client computers can use a volume. Clients
can’t browse for or mount SAN volumes on their own. You use Xsan Admin to unmount
a volume on clients that shouldn’t have access to it.
You can also set up access control lists (ACLs) in Xsan Admin or assign user and group
permissions to folders using standard file access permissions in the Finder.
Choosing RAID Schemes for LUNs
Much of the reliability and recoverability of data on a SAN is not provided by Xsan itself
but by the RAID arrays you combine to create your storage pools and volumes. Before
you set up a SAN, you use the RAID system configuration or administration application
to prepare LUNs based on specific RAID schemes.
WARNING: If a LUN belonging to an Xsan volume fails and can’t be recovered, all data
on the volume is lost. It is strongly recommended that you use only redundant LUNs
(LUNs based on RAID schemes other than RAID 0) to create your Xsan volumes.
LUNs configured as RAID 0 arrays (striping only) or LUNs based on single drives are
difficult or impossible to recover if they fail. Unprotected LUNs such as these should
only be used for volumes that contain scratch files or other data that you can afford
to lose.
30 Chapter 2 Planning a Storage Area Network
Loading...