Restore A Pair - HP XP P9500 User Manual

Restore a pair

If the pair is restored, the suspended data copy from the primary data volumes to the secondary
data volumes is resumed. If the delta resync pair is restored, the delta resync processing is
performed.
This section describes the pair resync operation. Also, the instructions are used when performing
the delta resync operation.
Prerequisite information
The pair resynchronizing operation is performed from the primary storage system only.
Pairs in PSUS or PSUE status is resynchronized.
Best practice is to resynchronize when I/O load is low. This reduces impact on performance.
Operations on multiple pairs in the same consistency mirror with different statuses may result
in suspension during high periods of write I/O.
Prerequisites for delta resync operation
The delta resync operation is executed by selecting delta-resync only options during the resync
operation. If executing delta resync, please observe the following.
Status of the delta resync pair must be HOLD or HOLDING. If the pair status is in HLDE status,
you can change the status to HOLD by performing the pairresync operation.
Status of the Continuous Access Synchronous secondary volume (S-VOL) must be SSWS.
The Continuous Access Journal S-VOL uses two mirror IDs; one for the pair for 3DC multitarget
pair, one for the pair for the delta resync.
◦ The status of the Continuous Access Journal pair S-VOL must be PAIR, PSUS, or PSUE.
◦ The status of the delta resync Continuous Access Journal pair S-VOL must be HOLD.
The data path between primary volume (P-VOL) and S-VOL must be available
If data in the restore journal exceeds 80% of capacity, old journal data is automatically
deleted. This can occur when the Continuous Access Journal pair is suspended and has not
been resynchronized for a long time. If the journal data that is not restored to the S-VOL of
Continuous Access Journal exceeds 80% of the journal volume capacity, the S-VOL cannot
be restored only copying the journal data to the restore journal volume in the Continuous
Access Journal secondary storage system. In this case, based upon journal option settings,
either the entire P-VOL is copied to the S-VOL or delta resync operation finishes without any
processing.
Even if the capacity of the journal data does not exceed 80% of the journal volume, the journal
data may be destroyed in the following cases:
◦ When you restore the Continuous Access Synchronous pair, then updated the P-VOL.
◦ When you restore the Continuous Access Journal pair between the primary storage system
and the Continuous Access Journal secondary storage system, then updated the P-VOL.
◦ When the retry processing occurs because of a delay of the P-VOL update.
When the update of the Continuous Access Synchronous S-VOL is delayed.
◦
The status of the Continuous Access Journal pair may become PSUS or PSUE if the pair is split,
or due to a failure to copy all necessary data during a delta-resync operation. If this is the
case, all the data may be copied from the P-VOL to the S-VOL regardless of the journal option
settings when a delta-resync operation is performed.
60 Pair operations