IBM DS6000 Manual Do Utilizador

IBM System Storage DS6000 Series: Copy Services with IBM System z

Many parameters can affect the performance of FlashCopy operations. It is important to 
review the data processing requirements and hence select the proper FlashCopy options. 

This chapter examines when to use the COPY versus the NOCOPY mode and where to 
place the FlashCopy source and target volumes/LUNs. We also discuss when and how to 
use 

 FlashCopy—which should definitely be evaluated for use in most 

applications. 

Before proceeding with the discussion of FlashCopy best practices, lets review some of the 
basic terminology we will be using in this chapter.

Server - A DS6000 has two servers—Server 0 and Server 1, one on each controller 
card—and each server independently provides major functions for the disk subsystem: 
Directing 

 for data transferring to and from host processors, managing

 

resources, and directing lower 

 for transferring data to and from physical 

disks. You can issue the 

 command to see the available servers.

Device Adapter (DA) - A physical component of the DS6000 that provides communications 
between the servers and the storage devices. The 

 command lists the available device 

adapters.

Rank - An array site made into an array which is then made into a rank. For the DS6000 a 
rank is a collection of 8 disk drive modules (DDMs). The 

 command displays detailed 

information about the ranks.

In general, you can achieve the best performance by distributing the load across all of the 
resources of the DS6000. In other words, you should carefully plan your usage so that the 
load is:

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Spread evenly across disk subsystems

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Within each disk subsystem, spread evenly across servers

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Within each server, spread evenly across device adapters

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Within each device adapter, spread evenly across ranks

Additionally, it is always best to locate the FlashCopy target volume on the same DS6000 
server as the FlashCopy source volume. It is also good practice to locate the FlashCopy 
target volume on a different device adapter (DA) than the source volume, but there are some 
cases where this is really a 

 decision. 

Another choice available is whether to place the FlashCopy target volumes on the same 
ranks as the FlashCopy source volumes. In general it is best not to place these two volumes 
in the same rank. Refer to Table 10-1 on page 113 for a summary of the volume placement 
considerations.

Note: This chapter is equally valid for System z volumes and open systems LUNs. In the 
following sections only the term 

 or 

 will be used, but the text is equally valid 

if the terms LUN and LUNs were used, 

.