IBM Flex System V7000 Expansion Enclosure 4939H29 사용자 설명서

Chapter 9. IBM Flex System V7000 Storage Node Copy Services 

Draft Document for Review January 29, 2013 12:52 pm

The link requirements are valid for Metro Mirror and Global Mirror. Basically, there are two link 
requirements:

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Round-trip latency

The total round-trip latency must be less than 80 ms, and less than 40 ms in each 
direction. Latency simulations should be performed with your applications before putting 
any network links in place to see if the applications perform at an acceptable level while 
meeting the round-trip latency requirement.

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Bandwidth

The bandwidth must satisfy the following requirements: 

– If you are not using Change Volumes: Be able to sustain peak write load for all mirrored 

volumes and background copy traffic.

– If you are using Change Volumes with Global Mirror: Be able to sustain change rate of 

Source Change Volumes and background copy traffic.

– Additional background copy rate (the best practice is 10% to 20% of maximum peak 

load) for initial synchronization and resynchronization.

– Remote Copy internal communication at idle with or without Change Volumes is 

approximately 2.6 Mbps. This amount is the minimum amount.

Figure 9-67 shows a table of the most common bandwidths available for wide area 
network (WAN) line types available in the industry.

Table 9-5 on page 396 lists which combinations of FlashCopy and Remote Copy are 
supported. 

Redundancy: If the link between two sites is configured with redundancy so that it can 
tolerate single failures, the link must be sized so that the bandwidth and latency 
requirement can be met during single failure conditions.