HP (Hewlett-Packard) AX696-96243 User Manual

HP StoreVirtual Storage Multi-Site Configuration Guide

Abstract

This guide contains detailed instructions for designing and implementing the Multi-Site SAN features of the LeftHand OS. The Multi-Site SAN features enable you to synchronously and automatically mirror data between geographic sites. Topics include designs for network configurations and instructions about implementing the network designs. The intended audience is system administrators who manage HP StoreVirtual Storage solutions.

For the latest version of this guide, see the HP website http://www.hp.com/support/StoreVirtualManuals.

HP Part Number: AX696-96243 Published: March 2013 Edition: 7

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The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein.

Acknowledgements

Microsoft, Windows, Windows XP, and Windows NT are U.S. registered trademarks of Microsoft Corporation.

1 Designing a Multi-Site SAN.........................................................................5

Designing the network for the Multi-Site SAN...............................................................................5

Best practices for implementing the Multi-Site SAN network.......................................................5

Common Multi-Site SAN network designs................................................................................6

Sample recommended network configurations for Multi-Site SANs..............................................7

Using multiple subnets .........................................................................................................9

Connecting volumes to multiple subnets in a Multi-Site SAN using the Microsoft iSCSI

initiator........................................................................................................................10

Using multiple cluster VIPs when connecting to a Multi-Site SAN..........................................10

Connecting application servers with single or multiple NICs to a Multi-Site SAN ...................10

Using MPIO with multiple subnets....................................................................................12

Configuring sites and managers to achieve optimal high availability and redundancy.....................12

Best practice.....................................................................................................................13

Sample configurations........................................................................................................13

Best practices for configuring quorum and managers in a Multi-Site SAN environment.....................15

Configuring data replication for optimal availability and redundancy............................................16

Using Network RAID-10+2..................................................................................................17

Setting up application clusters in a Multi-Site SAN environment.....................................................17

Using the Primary Site designation in two-site configurations........................................................17

Failure modes and recovery steps.........................................................................................17

Alternative setups....................................................................................................................18

2 Implementing a Multi-Site SAN...................................................................20

Before you begin....................................................................................................................20

Preparing to install a new Multi-Site SAN..............................................................................20

Preparing to convert an existing SAN to a Multi-Site SAN.......................................................20

Installing the Multi-Site SAN.....................................................................................................20

Creating the management group.........................................................................................21

Creating Multi-Site clusters and volumes................................................................................21

Using the Multi-Site cluster wizard...................................................................................21

Creating sites...........................................................................................................22

Viewing the Multi-Site cluster information..........................................................................22

Converting an existing SAN to a Multi-Site SAN.........................................................................23

Prerequisites......................................................................................................................23

Using the Multi-Site cluster wizard...................................................................................23

Configuring managers............................................................................................................24

Overview..........................................................................................................................24

Configuring regular managers.............................................................................................24

Fault tolerant manager configurations..............................................................................24

Installing and configuring a Failover Manager.......................................................................24

Best practice ................................................................................................................25

Adding the Failover Manager to the management group and site...................................25

Configuring sites....................................................................................................................25

Viewing sites in the CMC....................................................................................................26

Sites map view.............................................................................................................26

Designating a primary site..................................................................................................27

Adding a site....................................................................................................................27

Editing a site.....................................................................................................................27

To edit a site................................................................................................................27

Deleting a site...................................................................................................................27

Adding storage systems to a Multi-Site cluster.............................................................................28

Adding additional capacity to existing sites...........................................................................28

Contents 3

To add capacity............................................................................................................28

Removing storage systems from a Multi-Site cluster.......................................................................29

To remove the storage systems from the site...........................................................................29

Removing servers from a site....................................................................................................29

3 Support and other resources......................................................................30

Contacting HP........................................................................................................................30

Subscription service............................................................................................................30

Rack stability..........................................................................................................................30

Customer self repair................................................................................................................30

HP Insight Remote Support Software..........................................................................................30

Related information.................................................................................................................31

HP websites......................................................................................................................31

4 Documentation feedback...........................................................................32

Glossary....................................................................................................33

Index.........................................................................................................39

4 Contents

1 Designing a Multi-Site SAN

The HP StoreVirtual Multi-Site SAN features enable you to synchronously mirror data between sites automatically. You create a Multi-Site SAN by configuring equal numbers of storage systems into sites in the software.

The Multi-Site SAN software enables the following features:

• Multi-Site clusters that can:

Span up to three sites◦

◦ Span multiple subnets

◦ Have multiple VIPs

• Geographical awareness, enabled by designating storage systems as members of a particular

site.

• Synchronously replicated (mirrored) data between sites, based on volume data protection

level.

• Site information that ensures that data is mirrored between sites for high availability and

disaster recovery.

• I/O path preferencing, so that application servers connect to storage systems located in the

same site.

• Failover Manager support for automatic failover/failback in three-site configurations without

requiring a physical storage system in the third site.

• Failover Manager for quorum management if the network connection between the two sites

becomes unavailable. For information about the Failover Manager, see “Using the Failover Manager” in the HP StoreVirtual Storage User Guide.

• Failure protection through data replication, site design, and quorum managers. Multi-Site SAN

can protect against data center failures (power or network outages or a natural disaster) and individual storage system failures (power or network outages, a system disaster, or a system component failure).

Requirements

All sites must have the same number of storage systems. Storage systems must be added to or removed from Multi-Site clusters in equal numbers.

Designing the network for the Multi-Site SAN

Good network design is a critical part of setting up a Multi-Site SAN that meets your needs. A good Multi-Site SAN network encompasses the following attributes:

• Reliability

• High availability

• High performance

Best practices for implementing the Multi-Site SAN network

• Plan a single subnet for the Multi-Site SAN.

• Adequate bandwidth—Plan for 50 MB/sec of bandwidth for each storage system in each

site. For instance, if each site contains five storage systems, then you need 250 MB/sec throughput. In this case, that translates into two Gigabit Ethernet links, or more.

Designing the network for the Multi-Site SAN 5

• Low round-trip latency—In order to not impact disk I/O to the application server, the round-trip

latency between the sites must be no more than 2 ms.

• Redundant links—Have multiple physical connections (media) between the sites for redundancy.

The network should be configured so that a link failure does not cause the Multi-Site SAN to go offline.

• Assign servers to sites—Avoid high-latency connections by assigning application servers to

the site where the server is located. Application servers assigned to a site connect only to storage systems in the same site as follows:

◦ Without MPIO—With servers set up in the CMC with the load balancing option, the

system sets up the iSCSI session only to storage systems assigned to the same site.

◦ With MPIO and the HP StoreVirtual DSM for Microsoft MPIO—The system sets up iSCSI

sessions only to storage systems assigned to the same site.

◦ With MPIO and the Microsoft DSM—With servers set up in the CMC with the load

balancing option, the system sets up the iSCSI session only to storage systems assigned to the same site.

• Use the Failover Manager—Unless you have storage systems in three physical sites, use a

Failover Manager. Put the Failover Manager in the third site (physical or logical) located on a network that is isolated from the other sites and has a different power connection. Minimum requirement: 100 MBit/s with 5 MS latency. For information about the Failover Manager, see “Using the Failover Manager” in the HP StoreVirtual Storage User Guide.

Common Multi-Site SAN network designs

Based on the Multi-Site SAN configuration, there are many network designs that can be implemented that solve the redundancy, high availability, and performance requirements for the Multi-Site SAN. A few commonly used designs are:

• Dual redundant links between the sites

• Full-mesh triangular (three) redundant links between sites

• Hub and spoke central network core with redundant links out to each site

• Combination full-mesh core network with triangular (three) links between sites

Balancing the requirements for high availability during certain types of failures in the Multi-Site SAN and the budget associated with the network infrastructure typically dictates the network architecture you choose to implement. The most redundant network typically will cost the most to implement. However, not implementing redundancy in the Multi-Site SAN network significantly curtails the benefits of the Multi-Site SAN software. Table 1 (page 6) shows the common Multi-Site network configurations and the types of failures against which they provide protection.

Table 1 Common Multi-Site network configurations and failure protection of each

Dual redundant links between sites

intervention

Network failure protectionSite failure protectionNetwork topology

Storage system failure protection

YesYesYes, with manual

between sites

triangular links between sites

6 Designing a Multi-Site SAN

YesYesYesFull-mesh triangular links

YesHub and spoke central core

does not fail

YesYes, so long as the core

YesYesYesCombo full-mesh core with

Sample recommended network configurations for Multi-Site SANs

This section provides illustrations of common network configurations for the topologies described in Table 1 (page 6). The clusters and sites can have many more storage systems than are depicted in these illustrations, which focus on the network design.

Figure 1 Dual redundant links between two sites

1. Dual redundant GigE links

Figure 2 Dual redundant links between two sites with Failover Manager in logical third site

1. Dual redundant GigE links

2. Optional redundant path

Designing the network for the Multi-Site SAN 7

Figure 3 Triangular network with Failover Manager

1. Dual redundant GigE links

Figure 4 Hub and spoke network core with redundant links out to each site

1. Core network hub and spoke

8 Designing a Multi-Site SAN

Figure 5 Combination full-mesh core with triangular links to all sites

1. Full mesh core network

Using multiple subnets

IMPORTANT: Best practice is to use a single subnet in most cases.

You can use multiple subnets with a Multi-Site SAN. Multiple subnets let you have multiple VIPs, one VIP per subnet. The advantage of using multiple VIPs is that you can connect to a volume without having to leave the local subnet.

Alternatively, you can assign an application server to a site. Application servers assigned to a site connect only to storage systems in the same site. For more information, see “Best practices for

implementing the Multi-Site SAN network” (page 5).

If you use multiple subnets within the iSCSI cluster and implement one subnet per site, you can take advantage of the following Multi-Site SAN features:

• One Virtual IP address per site. iSCSI discovery sessions are terminated on a storage system

that is local to the application server in that site.

• Virtual IP addresses are hosted only on storage systems that reside in the same subnet as the

VIP.

• Read and Write I/O requests are forwarded from the application server to a storage system

that is in the same site as the server. This ensures that the I/O path is optimal and multiple network hops across the network link between the sites are eliminated.

Figure 6 (page 10) shows an example of how the Multi-Site SAN setup maps to subnets, VIPs, and

application servers.

Designing the network for the Multi-Site SAN 9

Figure 6 Multi-Site SAN mapping to subnets, VIPs, and application servers

1. Dual redundant GigE links

Connecting volumes to multiple subnets in a Multi-Site SAN using the Microsoft iSCSI initiator

Connecting to volumes in a multiple subnet configuration is similar to connecting to volumes in a single-site configuration, with the following important differences:

• You must configure all cluster VIPs for discovery, for proper failover/failback configuration of

a Multi-Site SAN. List the VIPs in the preferred order of connection. For example, if Site A is the first preference for connection, put the VIP associated to Site A first in the discovery list.

• You must also log on to the volumes with the default Target Portal setting.

Using multiple cluster VIPs when connecting to a Multi-Site SAN

Use the Virtual IP address of the cluster when connecting to volumes. In a multiple subnet configuration, you must enter both of the VIPs of the multi-site cluster on all the application servers. In addition, all the application servers must have the VIPs listed in the same order. A sample Multi-Site SAN configuration is shown in Figure 7 (page 11). In this configuration, the cluster has three sites: Site A, Site B, and Site C. Site A is primary.

Connecting application servers with single or multiple NICs to a Multi-Site SAN

1. On each application server, enter the cluster VIPs in the same order as on the Discovery tab

of the iSCSI Initiator Properties window.

10 Designing a Multi-Site SAN

Figure 7 Entering VIPs in a Multi-Site SAN configuration

2. On the Targets tab, select the volume to log on to.

3. Click Log On.

4. Select the Enable multi-path check box if using MPIO.

Figure 8 Logging on to volume

5. [Optional] If you want this volume to be available after rebooting, select the Automatically

restore... check box.

6. Click Advanced to open the Advanced Settings window.

7. Configure the Advanced Settings as follows:

• For Local adaptor, select Microsoft iSCSI initiator.

• For Source IP, select the IP address of the storage NIC to connect to the volume.

• For Target portal, leave as Default so that the Discovery list of VIPs is used in the same

order on all storage systems.

Designing the network for the Multi-Site SAN 11

Figure 9 Target portal value remains Default

8. After setting the values, click OK to close the Advanced Settings dialog.

9. Click OK again to finish logging on.

10. If you want to set the MPIO load balancing policy, see the HP StoreVirtual Storage DSM for

MPIO Deployment Guide.

11. If you have multiple NICs, repeat steps 1 through 10 for the additional NICs.

Using MPIO with multiple subnets

When you are using multiple subnets in a Multi-Site SAN, the HP StoreVirtual DSM for Microsoft MPIO or Microsoft DSM will only build I/O paths to the storage systems that are in the same subnet as the application server. See the HP StoreVirtual Storage DSM for MPIO Deployment Guide for more information about MPIO.

When using VMware ESX 4 or higher and its native MPIO in a Multi-Site SAN, you cannot configure more than one subnet and VIP. Multiple paths cannot be routed across subnets by the ESX/ESXi 4 initiator. With VMware vSphere, the preferred configuration is a single subnet and with vCenter servers assigned to sites in LeftHand OS.

Configuring sites and managers to achieve optimal high availability and redundancy

Several recommended site configurations can be used with the Multi-Site SAN software. These configurations provide varying levels of availability and redundancy. Table 2 (page 13) shows the recommended configurations. Select the one that best matches your environment.

12 Designing a Multi-Site SAN

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