IBM ProtecTier Implementation and Best Practices Guide

108 IBM ProtecTIER Implementation and Best Practices Guide

7.3.4 User data on SATA disks

The following statements apply specifically to the user data placed on SATA disks in the

ProtecTIER repository:

򐂰 RAID 5 is supported, but for new systems, RAID 6 (enabling dual-parity to sustain dual

disk failure) with 6+2 disk members is recommended for increased availability and faster

recovery from disk failure.

򐂰 For optimal performance, create at least 24 user data RAID groups.

򐂰 The size of user data RAID Groups/LUNs must be consistent. For example, do not mix

7+1 SATA user data LUNs with 3+1 SATA LUNs. Smaller disk groups hold back the

performance of the larger groups and degrade the overall system throughput. For

example, using storage from 2+2 or 4+1 RAID groups for the expansion might result in

performance degradation because of Input/Output Operations Per Second

(IOPS) bottlenecks.

򐂰 When using SATA disks, create LUNs with a maximum size of 6 TB. A bigger LUN

increases the amount of metadata and impacts the performance of your

ProtecTIER solution.

7.3.5 Expanding the repository

When expanding the repository, use the same spindle type and quantity of RAID groups for

metadata and user data. For example, if existing metadata LUNs were built on 4+4 RAID

groups, then new metadata RAID groups must be at least 4+4. In this example, if 2+2 or 4+1

RAID groups are used, it degrades overall system performance because of an

IOPS bottleneck.

7.4 Storage area network fabric

Although it is possible to directly connect ProtecTIER nodes to hosts (backup servers) and

storage arrays, you should connect the components into a storage area network (SAN) fabric.

The connection between ProtecTIER nodes and hosts is referred as a front-end connection,

and the connection between ProtecTIER nodes and storage arrays is referred as a back-end

connection. For the updated list of supported SAN switches of ProtecTIER, see the IBM

System Storage Interoperation Center (SSIC) at:

http://www-03.ibm.com/systems/support/storage/ssic

Important: Starting with ProtecTIER Version 3.2, the management of LUNs greater then 8

TB has been improved. When ProtecTIER V3.2 works with LUNs greater then 8 TB, it

splits them in to logical volumes of smaller size, which means that you can work with LUNs

greater then 8 TB. Be aware that there is no benefit in performance in doing this action.

You should always use RAID 6 for SATA or NL-SAS drives for the user data LUNs.

Chapter 7. Back-end storage overview 109

Figure 7-3 illustrates an example of SAN fabric and zoning.

Figure 7-3 Example of SAN fabric and zoning

7.4.1 Two Fibre Channel paths to each storage controller

Each ProtecTIER node has four Fibre Channel (FC) ports on the front-end FC Host Bus

Adapter (HBA) for host (backup application) connectivity and four FC ports on a back-end

HBA for back-end storage connectivity.

You should use two paths per storage controller.

7.4.2 Inter-Switch Link (ISL)

You should not use ISL between SAN switches connecting ProtecTIER nodes and storage

arrays. If ISL is used, ensure that it is not oversubscribed. Do not use ISL if IBM System

Storage DS3000, IBM System Storage DS4000®, or IBM System Storage DS5000 systems

are used as back-end storage.

7.4.3 Dedicated zones

You should connect a ProtecTIER node to your storage array If you are using SAN

peer-to-peer (P2P) topology. To connect a ProtecTIER node to a storage array, create

dedicated zones (one zone per initiator) for the ProtecTIER back-end port.

Fabric (1 or more SAN switches)

Backup Servers

(Host)

Storage Arrays

Backend Po rts

ProtecTIERNode

Controller A

Controller B

Zone E

Zone F

Zone G

Zone A

Zone B

Zone C

Zone D

Front-end connection -

Detail can be found in “Host

Attach ment ” Ch apter

Example of backend zoning with storage

array when SAN switches are used

Backend

connection

HBAs: When using only two back-end Fibre Channel links, use separate HBAs on the

TS7650G to avoid HBA hardware failure.

Important: Do not mix the back-end ports (QLogic) with front-end ports (Emulex) or any

other SAN devices in the same zone.