HP XP P9500 Storage - Manual (Page 73)

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 Suspend status are resynchronized.
•
Best practice is to resume the pair 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 Z secondary volume (S-VOL) must be Suspend.
•
The Continuous Access Journal Z 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 Z pair S-VOL must be Duplex or Suspended.
◦ The status of the delta resync Continuous Access Journal Z 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 Z pair is suspended and has not
been resynchronized for a long time. If the journal data that is not restored to the secondary
volume of Continuous Access Journal Z 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 Z secondary site. 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 Z pair, then updated the P-VOL.
◦ When you restore the Continuous Access Journal Z pair between the primary site and
the Continuous Access Journal Z secondary site, 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 Z S-VOL is delayed.
•
The status of the delta resync Continuous Access Journal Z pair might become Suspend by
splitting the pair or by failure while copying all data from P-VOL to S-VOL when the delta
resync Continuous Access Journal Z pair performs the operation as a Continuous Access
Journal Z pair before performing the delta resync operation. In this case, all data might be
copied from P-VOL to S-VOL regardless of the journal option settings when the delta resync
operation is performed.
Restore a pair 73