HP XP Business Copy Software - Manual (Page 15)

operation. For further information on RAID Manager, see the HP StorageWorks XP RAID
Manager User Guide.
•
Triggers for the change of pair status to PSUS
The performance in the state of PSUS(SP) or COPY(SP) is different depending on the value of
system option mode 459 (ON or OFF, OFF by default) and whether the S-VOL or the volume
in a pool that is associated with the S-VOL is an external volume or internal volume.
Table 1 Performance in PSUS(SP) or COPY(SP) vs. SOM 459 and S-VOL.
PSUS(SP) or COPY(SP) S-VOL* System option mode 459
The pair status changes to PSUS after
all the differential data are copied to
the cache in the storage system. Internal volume OFF
External volume
The pair status changes to PSUS after
all the differential data are copied to
the cache in the storage system, and
the destage in the external storage
system has completed. Internal volume ON
External volume
*If the S-VOL is a Dynamic Provisioning volume, it is the volume associated with the S-VOL in the pool volumes.
Suspend Pair Operation
When you suspend copy operations (using the RAID Manager pairsplit-E command), the P-VOL
and S-VOL status become PSUE and SSUE, respectively, and every track on the P-VOL is marked
as differential data. Performing pairresync on a suspended pair is similar to making an initial copy
and is not as fast as performing pairresync on a split pair.
The storage system will automatically suspend an XP Business Copy pair when it cannot keep the
pair mirrored for any reason. When the storage system suspends a pair, sense information is
generated to notify the host. The storage system will automatically suspend a pair under the following
conditions:
•
When the storage system detects an error condition related to an update copy operation.
•
When the differential bitmap in shared memory is lost (for example, due to offline microcode
exchange). This applies to COPY(SP) and PSUS(SP) pairs only. For PAIR, PSUS, COPY(RS),
or COPY(RS-R) pairs, the pair is not suspended but the entire P-VOL (S-VOL for reverse or quick
restore pairresync) is marked as difference data.
Resynchronize Pair Operations
To change the status of the pairs from PSUS to PAIR or from PSUE to PAIR, you must resynchronize
the pairs. XP Business Copy allows you to perform four different types of pairresync operations:
forward pairresync (Normal Copy and Quick Resync) and reverse pairresync (Reverse Copy and
Quick Copy). Forward pairresync means copying P-VOL data to the S-VOL, and reverse pairresync
means copying S-VOL data to the P-VOL.
•
Normal Copy (forward pairresync in normal speed)
The normal pairresync operation (see Figure 6 (page 17) ) first reads the differential bitmap
of the P-VOL and S-VOL, and then resynchronizes the S-VOL with the P-VOL based on the
differential bitmap. The copy direction for a normal pairresync operation is P-VOL to S-VOL.
Pair status changes to PAIR when the copying process of differential data completes. The pair
XP Business Copy Operations 15