Extended Update Cycles - Hitachi AMS 2000 User Manual

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Extended update cycles

If inflow to the P-VOL increases, all of the update data may not be sent
within the cycle time. This causes the cycle to extend beyond the user-
specified cycle time.
As a result, more update data in the P-VOL accumulates to be copied at the
next update. Also, the time difference between the P-VOL data and S-VOL
data increases, which degrades the recovery point value. In
failure occurs at the primary site immediately before time T3, for example,
data consistency in the S-VOL during takeover is P-VOL data at time T1.
When inflow decreases, updates again complete within the cycle time. Cycle
time should be determined according to a realistic assessment of write
workload, as discussed in
and bandwidth.
Hitachi AMS 2000 Family TrueCopy Extended Distance User Guide
Figure 1-2: Update Cycles and Differential Data
Chapter 2, Plan and design — sizing data pools
Overview
Figure 1-2, if a
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