HP XP P9500 Storage - Manual (Page 45)

Types of resync operation
Pairs can be resynchronized from primary volume to secondary volume and from secondary volume
to primary volume, as follows:
•
Normal Copy. Forward full resync, from primary volume to secondary volume.
The primary volume is accessible to hosts for both read and write operations. ◦
◦ The secondary volume is inaccessible to hosts.
•
Quick Resync. Forward resync from primary volume to secondary volume with no data copy.
Status changes to PAIR but with no resynchronization of data to the secondary volume.
◦ Differential data is copied to the secondary volume during update copying.
◦ The primary volume is accessible to hosts for read and write operations.
◦ Data in the primary and secondary volumes may not be the same after a Quick Resync
even when there is no host I/O during the operation. The pair must be split to ensure that
data is the same.
•
Reverse Copy. Reverse full resync from secondary volume to primary volume.
The primary volume is inaccessible to hosts. ◦
◦ All differential data is updated to the primary volume.
◦ Reverse Copy cannot be used for the following:
- Business Copy L2 pair
- Business Copy Z pair when the primary volume is shared with an FC Z/FCSE volume
•
Quick Restore, primary and secondary volumes are swapped. No data is copied, and the
pair is placed in PAIR status. Differential data is copied to the secondary volume during update
copy operations.
◦ Differential data is copied during update copying.
◦ The primary and secondary volumes are inaccessible during this operation. When the
operation completes, the primary volume becomes accessible.
◦ When there is a small amount of differential data between primary and secondary volumes,
the Reverse Copy operation may complete faster than Quick Restore.
◦ Performing LDEV maintenance during the Quick Restore process increases the time for
the operation to complete.
◦ Quick Restore cannot be used for the following:
- A Business Copy L2 pair
- A pair in which one volumes is a THP V-VOL, though not both
- A Business Copy pair whose primary volume is shared with a Snapshot volume
- A Business Copy Z pair whose primary volume is shared with an FC Z/FCSE volume
Prerequisite information for resynchronizing
•
For Normal Copy and Quick Resync, the secondary volume must be offline.
•
For Reverse Copy and Quick Restore, the primary volume must be offline.
•
For Normal Copy or Quick Resync, the pair must be in PSUS, PSUE, or PSUS(SP)/PSUS status.
Pair resynchronization 45