HP StorageWorks XP Remote Web Console Software - Manual (Page 19)

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NOTE: When adding pairs, you can select the pace for the initial copy operations: slower, medium, or
faster. The slower pace minimizes the impact of SI390 operations on disk array I/O performance while the
faster pace completes the initial copy operations as quickly as possible.
Figure 2 Adding a pair
Update Copy Operation
The SI390 update copy operation updates the T-VOL of an SI390 pair after the initial copy operation is
complete. Because an S-VOL remains available to all hosts for read and write I/Os during initial copy, the
S-VOL might be updated during the operation. Therefore, when the status of the pair changes to Duplex
after the initial copy operation is complete, the update copy operations take place and the differential data
of the S-VOL is copied to the T-VOL. As write I/Os are performed on a duplex S-VOL, the
XP128/XP1024/XP10000/XP12000 stores a map of the S-VOL differential data, and then performs
update copy operations periodically based on the amount of differential data present on the S-VOL as well
as the elapsed time between update copy operations. The following figure illustrates an update copy
operation in an SI390 pair with only one T-VOL.
CAUTION: Even if the copy operation is completed without any host I/O, the data in the S-VOL and the
data in the T-VOL may not be the same. Whether the S-VOL and the T-VOL have the same data depends on
the condition of the disk array. To make the S-VOL data and the T-VOL data equal, split the pair and make
the pair status split.
NOTE: Update copy operations are not performed for SI390 pairs with the following status: pending,
SP-pend, V-Split, split, resync, resync-R, and suspend.