HP D2D4100, D2D4300, D2D2500 User Manual
HP StoreOnce
Backup System Concepts Guide
Abstract
If you are new to the HP StoreOnce Backup System, it is a good idea to read this guide before you configure your system. It
describes the StoreOnce technology and advises how to plan the workload being placed on the HP StoreOnce Backup System
in order to optimize performance and minimize the impact of deduplication, replication and housekeeping operations competing
for resources.
IMPORTANT: The localized versions of this guide have been produced prior to launch. The English version that is available
on the web at launch may have later updates. Always check http://www.hp.com/support/manuals for the most up-to-date
documentation for your product.
HP Part Number: EH985-90915
Published: February 2011
Edition: 1
© Copyright 2011 Hewlett-Packard Development Company, L.P.
Confidential computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212, Commercial
Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under
vendor's standard commercial license.
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.
WARRANTY STATEMENT: To obtain a copy of the warranty for this product, see the warranty information website:
http://www.hp.com/go/storagewarranty
Linear Tape-Open, LTO, LTO Logo, Ultrium and Ultrium Logo are trademarks of Quantum Corp, HP and IBM in the US, other countries or both.
Microsoft, Windows, Windows NT, and Windows XP are U.S. registered trademarks of Microsoft Corporation.
Intel and Itanium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries.
AMD is a registered trademark of Advanced Micro Devices, Inc.
Contents
1 Before you start..........................................................................................5
Overview................................................................................................................................5
NAS targets for backup applications...........................................................................................5
Virtual Tape Library targets for backup applications......................................................................5
Comparing NAS and Virtual Tape Library targets.........................................................................6
Connecting to the HP StoreOnce Backup System...........................................................................6
For more information.................................................................................................................6
2 Virtual Tape Devices...................................................................................7
Overview................................................................................................................................7
Emulation types........................................................................................................................7
Creating and configuring virtual tape devices...............................................................................8
Limitations on the number of devices.......................................................................................8
Flexible emulation (G2 products only)..........................................................................................9
VTL devices on an Ethernet network...........................................................................................10
Backup applications and Replication Target libraries...............................................................11
VTL devices on Fibre Channel...................................................................................................11
Fibre Channel topologies....................................................................................................11
Zoning.............................................................................................................................12
3 NAS shares.............................................................................................13
Operating system support........................................................................................................13
Backup application support......................................................................................................13
Maximum number of NAS shares.............................................................................................13
Maximum number of files per NAS share and appliance.............................................................13
Maximum number of users per CIFS share.................................................................................14
Maximum number of hosts per NFS share (G2 products only).......................................................14
4 Data deduplication...................................................................................15
What is data deduplication?....................................................................................................15
Data deduplication and the HP StoreOnce Backup System...........................................................15
Tape rotation example with data deduplication ..........................................................................16
5 Replication..............................................................................................18
Replication overview...............................................................................................................18
HP StorageWorks Replication Manager (HP D2D4xxx Series only)................................................19
Replication concepts and terminology.......................................................................................20
Replication deployment strategies.............................................................................................26
Replication Licensing...............................................................................................................28
Seeding the Target Appliance..................................................................................................29
Recovering a Source Appliance................................................................................................30
6 Housekeeping..........................................................................................33
What is housekeeping?...........................................................................................................33
What effect does housekeeping have on performance?...............................................................33
Why is housekeeping important?..............................................................................................33
What do I need to do?............................................................................................................33
Contents 3
For more information...............................................................................................................34
7 Performance............................................................................................35
Optimizing peformance...........................................................................................................35
Balancing performance and deduplication ratios........................................................................35
To be avoided........................................................................................................................36
Glossary....................................................................................................37
A Tape Attach information for G1 products.....................................................41
Options for archiving to tape....................................................................................................41
Archiving methods..................................................................................................................42
Cartridge copy..................................................................................................................42
Cartridge export................................................................................................................43
Compression.....................................................................................................................45
Cartridge import................................................................................................................45
Tape spanning .................................................................................................................46
Replication and Tape Attach....................................................................................................46
About this guide..........................................................................................48
Intended audience..................................................................................................................48
Related documentation............................................................................................................48
Document conventions and symbols..........................................................................................48
HP technical support...............................................................................................................49
Customer self repair................................................................................................................49
Registering your HP D2D Backup System....................................................................................49
Subscription service................................................................................................................49
HP websites...........................................................................................................................50
Documentation feedback.........................................................................................................50
Index.........................................................................................................51
4 Contents
1 Before you start
In this chapter:
• Overview
• NAS targets for backup applications
• Virtual Tape Library targets for backup applications
• Comparing NAS and VTL targets
• Connecting to the HP StoreOnce Backup System
• For more information
Overview
The HP StoreOnce Backup System is a disk-based storage appliance for backing up host network
servers or PCs to target devices on the appliance. These devices are configured as either
Network-Attached Storage (NAS) or Virtual Tape Library (VTL) targets for backup applications.
The total number of backup targets provided by an HP D2D Backup System is split between VTL
and NAS devices and varies according to model.
These devices may be all VTL, all NAS or any combination of NAS and VTL devices. All HP
StoreOnce devices automatically make use of StoreOnce deduplication, ensuring efficient and
cost-effective use of disk space.
NAS targets for backup applications
Support for both CIFS and NFS protocols means that NAS target devices may be created as backup
targets for both Windows and UNIX/Linux hosts, and may be used with most backup applications
that support backup to disk. NAS targets on an HP D2D Backup System provide network file share
access that is optimized for backup to disk. They should not be used for general purpose file
storage.
Virtual Tape Library targets for backup applications
The backup target appears to the host as an Ultrium Tape Library and requires a backup application
that supports backup to tape. Tape Library emulation type is selected during initial configuration
and this determines the number of cartridge slots and embedded tape drives that may be configured
for the device.
Virtual Tape Libraries provide considerable flexibility for a variety of backup rotation schemes.
The HP D2D4100 and D2D4300 Series may be configured with iSCSI and Fibre Channel (FC)
devices. (The HP D2D4106i Backup System does not support FC.) The HP D2D2500 Series is
configured with iSCSI devices.
The default configuration emulates:
• HP D2D2500 Series: HP StorageWorks 1/8 G2 Ultrium Tape Autoloader
• HP D2D4100 and D2D4300 Series: HP StorageWorks MSL2024 Tape Library
Overview 5
NOTE: The HP D2DBS Generic Library emulation type provides the most flexibility in numbers
of cartridges and drives. It is also clearly identified in most backup applications as a virtual tape
library and so is easier for supportability. If your backup application supports this emulation type,
it is the recommended option.
Comparing NAS and Virtual Tape Library targets
The following table summarizes some of the differences between NAS targets and Virtual Tape
devices.
Table 1 Comparing NAS targets and Virtual Tape devices
NAS targetsVirtual tape devices
Enables use of backup application functionality that is only
available with file shares, such as Disk-to-Disk-to-Tape
implementations.
Acts as a staging post to tape because backups are in tape
format; supports direct tape offload
May be used with backup applications that do not support
backup to tape
Requires a backup application that supports backup to
tape
Requires a new backup job, but is simple to set upIntegrates into the current backup routine and requires no
special backup jobs
No special licences are required in most cases, potentially
saving money
May require purchase of a 'tape backup' licence for the
backup application
Connecting to the HP StoreOnce Backup System
The Web Management Interface is the main tool for accessing and configuring the HP StoreOnce
Backup System and its devices. However, you can also connect to the appliance using a system
console and keyboard or the iLO2 management port.
For more information
Separate chapters in this guide provide more background information about VTL and NAS devices
and the specifications that are supported. For information about using the Web Management
Interface to configure and monitor devices, refer to the HP StoreOnce D2D Backup System user
guide.
6 Before you start
2 Virtual Tape Devices
In this chapter:
• Overview
• Emulation types
• Creating and configuring Virtual Tape Devices
• VTL devices on an Ethernet network
• VTL devices on Fibre Channel
Overview
Virtual Tape Devices are backup targets on the HP StoreOnce Backup System to which the backup
application on the hosts write data. They appear to the host as a locally-attached physical tape
library or autoloader, but physically, they use disk space on the HP StoreOnce Backup System
which, as in tape terminology, is referred to as slots or cartridges.
Each storage slot contains a cartridge. The difference between an autoloader and a library is that
a library can support multiple tape drives whereas an autoloader only has one tape drive. Libraries
provide considerable storage capacity and full support for tape rotation strategies. (It may be
necessary to upgrade your backup application to support libraries.)
Emulation types
The HP D2D Backup System supports a wide range of library and drive emulation types. The
options available vary according to the HP D2D Backup System model. If the emulation type is not
in the dropdown list on the Devices page of the Web Management Interface, it is not supported
on your model. For example, HP D2D2500 Series do not support the ESL-e and EML-e Library
emulation types.
• D2DBS Generic Library: This is a tape library device which allows you to configure many
drives per library and many cartridges per library
G2 products
◦ HP D2D2502/2504: up to 16 (HP D2D2502) and 32 (HP D2D2504) drives per library
and up to 96 cartridges per library
◦ HP D2D4106/4112: up to 64 (HP D2D4106) and 96 (HP D2D4112) drives per library
and up to 1024 cartridges per library
◦ HP D2D4312 and HP D2D4324: up to 200 drives per library and up to 4096 cartridges
per library
Discontinued G1 products
◦ HP D2D2503: one drive per library and up to 48 cartridges per library
◦ HP D2D2502/2504: up to four drives per library and up to 48 cartridges per library
◦ HP D2D4004/4009: up to four drives per library and up to 96 cartridges per library
◦ HP D2D4112: up to four drives per library and up to 144 cartridges per library
If it is supported by your backup application, this is the preferred emulation type to be used
because it does not emulate any physical library types in existence and is, therefore, clearly
identifiable as a D2D device. It is the most flexible emulation type available; however, backup
application support varies by software vendor.
If you have selected D2DBS Generic for the Library Emulation Type, you will be able to select
Ultrium VT for the drive emulation. This is a generic Ultrium device which is clearly identifiable
Overview 7
as virtual. Backup application support for Ultrium VT is reasonable, but not quite as complete
as the D2DBS library type, so it is not possible to use it with all backup software.
NOTE: Symantec prefer their customers to use this emulation type with BackupExec and
Netbackup.
• HP 1x8 G2 Autoloader: This is a single Ultrium tape drive autoloader with a maximum of 24
cartridge slots. It should be used for simple rotation schemes where a single backup job is to
run at a time. This emulation type is widely supported by backup applications.
• MSL G3 series (2x24) Library: This is a tape library device with a maximum of two embedded
Ultrium tape drives and 24 cartridge slots. It should be used when implementing rotation
schemes which involve simultaneous backup jobs to two devices. This emulation type is widely
supported by backup applications.
• MSL G3 series (4x48) Library: This is a tape library device with a maximum of four embedded
Ultrium tape drives and 48 cartridge slots. It should be used when implementing rotation
schemes which involve simultaneous backup jobs to more than two devices or those that use
a large number of cartridges devices. This emulation type is widely supported by backup
applications.
• MSL G3 series (8x96) Library: This is a tape library device with a maximum of four embedded
Ultrium tape drives and 96 cartridge slots.
• ESL-E series Library: This is an enterprise tape solution which allows you to configure many
drives per library and many cartridges per library (see values for D2DBS emulation above).
Use the Show Details Box at the top of the screen to view maximum details and actual numbers
used.
• EML-E series Library: This is an enterprise tape library solution which allows you to configure
many drives per library and many cartridges per library (see values for D2DBS emulation
above). Use the Show Details Box at the top of the screen to view maximum details for drives
and libraries and actual numbers used.
Creating and configuring virtual tape devices
Virtual tape devices may be created in two ways:
• If you are creating iSCSI devices on Windows, the installation wizard will automatically create
a virtual tape library for you. The default settings also create a library automatically for any
host that connects using iSCSI, even if the wizard is not run. (This feature can be disabled.)
• New libraries and all FC libraries are created from the Virtual Tape Devices — Devices page
of the Web Management Interface, which is also used to configure devices and slots.
When you configure your HP StoreOnce Backup System with a tape library, the drive emulation
type that you select determines the default cartridge size for each configured slot. LTO-2 defaults
to 200 GB, LTO-3 defaults to 400 GB, LTO-4 defaults to 800 GB and LTO-5 defaults to 1600 GB.
This is the equivalent of a tape library with multiple slots, each containing a 200, 400, 800 or
1600 GB cartridge. Both tape spanning and, more importantly, flexible tape rotation strategies
are possible.
NOTE: All LTO default configurations can be configured with larger or smaller cartridge sizes.
Limitations on the number of devices
An important consideration when configuring VTL devices is that the library and each drive that
you configure for it counts as a separate device. There are practical limitations on the number of
devices that each host and FC switch or HBA can access.
For iSCSI VTL devices a single Windows or Linux host can only access a maximum of 64 devices.
A single library with 63 drives is the most that a single host can access. Configuring a single library
8 Virtual Tape Devices
with more than 63 drives will result in not all devices in the library being seen (which may include
the library device). The same limitation could be hit with multiple libraries and fewer drives per
library.
IMPORTANT: The maximum number of devices per appliance also impacts on the number of
NAS shares that you can configure. For example: if you configure 250 devices on the HP D2D4312
or D2D4324, you will not be able to configure NAS shares. See also Flexible emulation.
Table 2 Maximum number of libraries and drives per G2 appliance
HP D2D4324HP D2D4312HP D2D4112HP D2D4106HP D2D2504iHP D2D2502i
5050241684Max libraries
20020096643216Max drives per
library
250250120804020Max devices
per appliance
40964096102410249696Max slots per
library
(D2DBS)
NOTE: Apart from the HP D2D2502i, it is possible to exceed the maximum physical limitation
when configuring any of the above models.
Table 3 Maximum number of libraries and drives per G1 appliance
HP D2D4112
HP D2D4004
/4009HP D2D2504iHP D2D2503iHP D2D2502i
2416864Max libraries
44414Max drives per
library
14496484848Max slots per
library (D2DBS)
NOTE: It is only possible to exceed the maximum physical limitation when configuring the HP
D2D4112 Backup System.
Flexible emulation (G2 products only)
If supported, the ESL, EML and D2DBS emulations are particularly flexible because they allow you
to configure a large number of drives per library. This has two main benefits:
• It allows for more concurrent streams on backups which are throttled due to host application
throughput, such as multi-streamed backups from a database.
• It allows for a single library (and therefore dedupe store) to contain similar data from backups
that must run in parallel to increase deduplication ratio.
If using these flexible emulation types, the following factors should also be considered:
• Although there are no hard limits on the number of drives that can be configured per library,
there are limits on the total number of devices and shares that can be configured on an
Flexible emulation (G2 products only) 9
appliance. If you configure 1 library with 200 drives on an HP D2D4312 Backup System,
you will still have 49 libraries available in theory, but you will have no more drives.
• The total value also applies to NAS shares. If you configure the full 250 value as VTL devices,
you will not be able to configure any NAS shares for that appliance.
• Please refer to the D2D Best Practices for VTL, NAS and Replication implementations for
maximum and recommended values.
NOTE: G1 products do not support flexible emulation; they have fixed values for the above
emulation types (some products do not support all emulation types).
VTL devices on an Ethernet network
Each emulated backup device is uniquely mapped to an individual host; this is the network server
or PC that you wish to back up.
• The backup device appears to the host as a locally-attached tape autoloader or library.
• The backup device is accessed and managed from the backup software running on the host.
• The backup device is not visible to other devices on the network.
• Multiple servers may not back up to a single backup device.
Figure 1 shows a configuration with a single host. The Installation wizard has been run on Host
1. The HP D2D Backup System automatically generates a library for the host. The user may specify
the number of slots during installation.
Figure 1 Device configuration with one host
• By default, only one device is visible to the host, the iSCSI library that has been configured
for it during installation. Data from each host goes to its corresponding iSCSI library.
• Each backup device is visible only to the host for which it has been configured.
• A host may have multiple devices configured for it on the HP D2D Backup System, but this
means fewer hosts may be connected (not illustrated).
Figure 2 shows a configuration with three hosts. The Installation wizard automatically generates
a library for each host. The user may specify the number of slots during installation.
10 Virtual Tape Devices
Figure 2 Device configuration with multiple hosts
Backup applications and Replication Target libraries
Replication Target libraries are not normally visible to the host, but you can configure devices to
make them visible to backup applications.
There are two occasions when it may be useful to make a target library visible to the backup
application on the host.
• To confirm that replication is working correctly and check the integrity of the replicated backup
by doing a test restore
• To perform manual tape copy jobs to a tape device on the network using the backup application
See the HP StoreOnce D2D Backup System user guide for more information about using this feature.
VTL devices on Fibre Channel
FC Library devices on the HP D2D cannot be created for a specific host during installation; they
must be created using the Web Management interface. When you assign a library to a FC port
(port 1 or port 2) it becomes visible on the FC SAN. When you log in, you log in to the switch to
which the host is connected, which means that the library is visible to all other devices on the SAN.
You can zone your network so that only specific devices have access to it, but generally it is visible
to all.
NOTE: Fibre Channel is not supported on the HP D2D4106i or the HP D2D2500 Series Backup
System.
Fibre Channel topologies
The HP StoreOnce Backup System supports both switched fabric and direct attach (private loop)
topologies. A direct attach (point-point) topology is not supported.
A switched fabric topology utilizes one or more fabric switches to provide a flexible configuration
between several Fibre Channel hosts and Fibre Channel targets such as HP StoreOnce Backup
Systems.
Switched fabric configurations are implemented with Fibre Channel switches. Switches may be
cascaded or meshed together to form larger fabrics.
VTL devices on Fibre Channel 11
A direct attach topology is implemented by connecting the HP StoreOnce Backup System directly
to a Host Bus Adapter (HBA). In this configuration the Fibre Channel private loop protocol must
be used.
The preferred topology for the HP StoreOnce Backup System is switched fabric using NPIV (N_Port
ID Virtualisation).
NOTE: Please refer to http://www.hp.com/go/connect or http://www.hp.com/go/ebs for the
latest information.
Zoning
Zoning is only required if a switched fabric topology is used.
Due to complexities in multi-hosting tape devices on SANs, it is best to make use of zoning tools
to help keep the backup/restore environment simple and less susceptible to the effects of changing
or problematic SANs.
Zoning provides a way for servers, disk arrays, and tape libraries to see only those hosts and
targets that they need to see and use. The benefits of zoning include but are not limited to:
• Limiting unnecessary discoveries on the HP StoreOnce Backup System
• Reducing stress on the HP StoreOnce Backup System and its library devices by polling agents
• Reducing the time it takes to debug and resolve anomalies in the backup/restore environment
• Reducing the potential for conflict with untested third-party products
Zoning may not always be required for configurations that are already small or simple. Typically
the bigger the SAN is, the more zoning is needed. HP recommends the following for determining
how and when to use zoning.
• Small fabric (16 ports or less)—may not need zoning.
• Small to medium fabric (16 - 128 ports)—use host-centric zoning. Host-centric zoning is
implemented by creating a specific zone for each server or host, and adding only those storage
elements to be utilized by that host. Host-centric zoning prevents a server from detecting any
other devices on the SAN or including other servers, and it simplifies the device discovery
process.
• Disk and tape on the same pair of HBAs is supported along with the coexistence of array
multipath software (no multipath to tape or library devices on the HP StoreOnce Backup System,
but coexistence of the multipath software and tape devices).
• Large fabric (128 ports or more)—use host-centric zoning and split disk and tape targets.
Splitting disk and tape targets into separate zones will help to keep the HP StoreOnce Backup
System free from discovering disk controllers which it doesn't need to see. For optimal
performance, where practical, dedicate HBAs for disk and tape.
NOTE: Overlapping zones are supported.
12 Virtual Tape Devices
3 NAS shares
In this chapter:
• Operating system support
• Backup application support
• Maximum number of NAS shares
• Maximum number of files per NAS share and appliance
• Maximum number of hosts per NFS share
NOTE: It is important to understand that the HP StoreOnce network share is intended to be used
ONLY by backup applications that “back up to disk”. Do not use the NAS target device as a
drag-and-drop general file store. The one exception to this rule is if you are using the NAS share
to seed an appliance for replication.
Operating system support
Two interfaces are supported:
• a CIFS interface for Windows networks
• a NFS interface for Linux and UNIX networks
NOTE: G1 HP D2D Backup Systems support only the CIFS interface for Windows networks.
See the HP StoreOnce Backup System user guide for more information about using the Web
Management Interface to create and configure NAS shares as targets for backup applications.
Refer to the UNIX and Linux Configuration Guide for more information about the NFS interface.
Backup application support
NAS shares may be used with most applications that support backup to disk, including embedded
applications, such as Oracle RMAN and VMWare VCB Agent. For the most up-to-date information
about supported applications, refer to http://www.hp.com/go/connect and http://www.hp.com/
go/ebs.
Maximum number of NAS shares
The total number of “devices” provided by a StoreOnce appliance is split between VTL devices
and NAS shares. These devices may be all VTL, all NAS or any combination of NAS and VTL
devices.
Maximum number of files per NAS share and appliance
The HP StoreOnce NAS implementation is optimized for use with backup applications. These
applications create large backup files on the NAS share, which make much more efficient use of
deduplication than simply copying files of various sizes to a deduplicating share. To improve
performance for small metadata files created by backup applications and to allow random access
to the header information at the beginning of backup files, the first 24 MB of any backed up file
will not be deduplicated. This non-deduplicated region is called the deduplication threshold.
The HP StoreOnce Backup System imposes a limit on the number of files that can be stored on
each NAS share. The limit is 25000 files, which provides the ability to protect a large amount of
data using a backup application. The limit is imposed in order to allow efficient use of data
replication.
Operating system support 13
There are also limits on the number of open files greater than the deduplication threshold that are
allowed per share and per appliance. These are the files that hold the backed-up data.
Backup applications generally create a small number of additional files during a backup job in
order to store configuration details and catalog entries. Some of these small files will generally be
updated throughout the backup process and, in most instances, these files will be below the
deduplication threshold. So, there is also a maximum number of open files that are the same size
or smaller than the deduplication threshold that are allowed per appliance.
Across the whole HP StoreOnce Backup System the number of simultaneously open files is as
follows:
Table 4 Maximum number of files G2 products
HP D2D4324HP D2D4312HP
D2D4106/4112
HP D2D2504HP D2D2502
2500025000250002500025000Max files per share
64064012811296Max Total Open files
per appliance
128128644832Max Open files >24
MB per appliance
Table 5 Maximum number of files G1 products
HP D2D4112HP D2D4004/9HP D2D2504HP D2D2503HP D2D2502
2500025000250002500025000Max files per share
112401124096Max Total Open files
per appliance
4824481632Max Open files >24
MB per appliance
Maximum number of users per CIFS share
The maximum number of users that may be configured when using “user” or AD authentication for
access to a CIFS share is 50. This maximum is the total number of users per CIFS server and also
the maximum that can be allocated access to any single CIFS share
Different users may access single NAS shares simultaneously, however, a file within a share may
only be opened by one user at a time.
Maximum number of hosts per NFS share (G2 products only)
The maximum number of host systems that may be configured to access an NFS share is 50.
This maximum is the total number of hosts per NFS server and also the maximum that can be
allocated access to any single NAS share. A file within a share may only be opened by one user
at a time.
14 NAS shares
4 Data deduplication
In this chapter:
• What is data deduplication?
• Data deduplication and the HP D2D Backup System
• Tape rotation example with data deduplication
What is data deduplication?
Data deduplication is a process that compares blocks of data being written to the backup device
with data blocks previously stored on the device. If duplicate data is found, a pointer is established
to the original data, rather than storing the duplicate data sets. This removes, or “deduplicates,”
the redundant blocks. The key part of this is that the data deduplication is being done at the block
level and not at the file level which reduces the volume of data stored significantly.
Figure 3 Data stored after deduplication
The importance of the Index files
As a backup stream arrives at the HP StoreOnce Backup System the stream of data is “chunked”
into nominal 4K chunks, a hashing algorithm is run on each of these 4K chunks and this produces
a unique digital fingerprint which is written to an index file.
This process is repeated real time for every chunk of data involved in the first backup stream. When
subsequent backups run it is highly likely they will create identical hash codes, in which case the
hash count in the index is increased; the data associated with the hash code is not stored again
because it already resides in the Deduplication Store. So we only store the data once for any given
hash code – hence StoreOnce.
The Index files contain the mapping for the hashed data chunks created by deduplication and are
the main point of reference accessed and updated by both replication and housekeeping. Without
them, data cannot be restored successfully.
Data deduplication and the HP StoreOnce Backup System
Data deduplication is applied per library device or share. When you configure the library or share,
it defaults to deduplication enabled. It cannot be disabled on any G2 product. (On HP D2D2500
G1 and D2D4000/4009 machines, it may be disabled on virtual tape libraries, but not on NAS
shares.)
A device is associated with a host server and deduplication allows a greater amount of backup
history to be stored for that host. A larger number of full backups can be achieved, which makes
possible a rotation strategy with a longer retention history. It does not increase the number of host
servers that may be connected. The deduplication factor that has been applied to a device is
What is data deduplication? 15
calculated and displayed on the Web Interface. This figure is dynamic, it updates automatically
as more data is written to the device.
Benefits of HP D2D deduplication
The main benefit is that it is possible to store more data and retain data for longer on each device.
The host using the device has access to a greater depth of historical data that would otherwise
have been archived offline.
Deduplication:
• Provides efficient use of storage capacity by eliminating duplicate data
• Reduces disk expenditures by reducing storage space required. You can get more backups
for each host on the same size of storage (HP StoreOnce device)
• Prolongs disk data retention periods
• Reduces the volume of data that must be sent across a WAN for remote backups, replication,
and disaster recovery – reducing both risk and operational costs
See Replication for more information about replication.
Deduplication and compression
Compression is applied as part of deduplication. You can expect 1.6:1 compression even on the
first backup where no (or only a small amount of) deduplication can occur.
Tape rotation example with data deduplication
The two most significant factors affecting the deduplication ratio for backup are:
• How long do you retain the data?
• How much data changes between backups?
The following example shows projected savings for a 1 TB file server backup.
Retention policy
• 1 week, daily incrementals (5)
• 6 months, weekly fulls (25)
Data parameters
• Data compression rate = 2:1
• Daily change rate = 1% (10% of data in 10% of files)
Typical savings
The following table illustrates a reduction of approximately 11:1 in data stored. In practice,
assuming 1.25 TB is available for backup for this library, this means:
• Without data deduplication: only two weeks of data retention is possible before it is necessary
to archive data offline.
• With data deduplication: even after six months less than 1.25 TB of disk space has been used.
The following table illustrates how this affects the space required to store the data over 25 weeks.
The figures are used to generate the graph shown after the table.
16 Data deduplication
Loading...