444 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
9.2.7 Data Migrator
The Data Migrator (DM) process involves scheduling and the actual movement, or migration,
of the volume’s extents up to, or down from, the high disk tier.
The extent migration rate is described.
Easy Tier cycles moves extents at a rate of approximately 12 GB every 5 minutes as a
maximum speed:
This speed is applied to all functions except warm promotes and warm demotes.
If an Easy Tier cycle can generate cold demotes among the other operations, the speed is
reduced to 11GB every 5 minutes.
If an Easy Tier cycle has only cold demotes to be performed, the full 12GB limit can be
used.
This rate equates to around 3 TB a day that is migrated between disk tiers. Figure 9-5 shows
the Easy Tier Data Migrator flow.
Figure 9-5 Easy Tier Data Migrator
9.2.8 Easy Tier accelerated mode
Under normal production conditions, Easy Tier works properly to process daily workloads.
Easy Tier considers migration scenarios and scenarios where large amounts of data need to
be rebalanced in its internal algorithms.
Easy Tier accelerated mode was introduced in Storwize version 7.5. Easy Tier accelerated
mode allows the system to cope with migration situations where the user needs to speed up
the Easy Tier function temporarily.
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