HP XP Business Copy Software - Manual (Page 49)

system’s I/O performance and the SIz operations when you decide the number or structures
of pairs and their copy pace.
For example, assigning three T-VOLs to each S-VOL takes more resources than assigning only
one or two. More T-VOLs you assign on an S-VOL, the risk of affection on the I/O performance
of the storage system increases.
Even if you assign only one T-VOL on an S-VOL, pace of the initial copy operations may affect
the I/O performance of the storage system. Using a slower copy pace minimizes the impact
of SIz operations on I/O performance, while a faster copy pace produces point-in-time copies
more quickly but may affect I/O performance.
•
Load sharing of parity groups:
SIz S-VOLs or T-VOLs should not be concentrated in the same parity group. To disperse
workloads of the parity groups, each parity group should have both S-VOLs and T-VOLs evenly
distributed. SIz pairs for which an SIz operation is performed simultaneously should be in
different parity groups. If SIz pairs are concentrated in only a few parity groups, the host I/O
performance may be degraded. To minimize effect on the host I/O performance, take the
following actions:
◦ Specify Slower for the copy pace when you create, split, or resynchronize SIz pairs.
◦ If SIz pairs that you want to perform copy operation are in the same parity group, reduce
the number of pairs at one copy operation. For example, to split multiple SIz pairs in the
same parity group, wait until one pair is completely split before splitting another pair.
If the XP storage system is overloaded, you must increase cache, disk adapters, and/or parity
groups. HP recommends that SIz T-VOLs are assigned in the newly installed parity groups. If
you continue SIz operations with an overloaded storage system, host I/O performance may
be degraded.
•
When you resynchronize a pair by Quick Restore:
During the quick restore operation, the RAID levels, Cache Residency Manager for Mainframe
settings, and HDD types of the S-VOL and T-VOL are exchanged. For example, if the S-VOL
has a RAID-1 level and the T-VOL has a RAID-5 level, the quick restore operation changes the
RAID level of the S-VOL to RAID-5 and of the T-VOL to RAID-1. This also applies to RAID-6
volumes. To avoid any performance impact due to the quick restore operation:
◦ Make sure that the S-VOL and T-VOL have the same RAID level and HDD type before
performing the quick restore operation. To restore the original RAID levels after quick
restore, stop host I/Os to the pair, split the pair, perform the quick restore operation for
that pair again, and then restart the host I/Os to the pair.
◦ Because the Cache Residency Manager for Mainframe settings are exchanged during a
quick restore operation, you must perform one of the two following operations:
– Set the same Cache Residency Manager for Mainframe settings (locations) for the
S-VOL and T-VOL before performing the quick restore operation.
– Release the Cache Residency Manager for Mainframe settings of the S-VOLs and
T-VOLs before the quick restore operation, and then reset the Cache Residency
Manager for Mainframe settings of the S-VOLs and T-VOLs after the pair status
changes to duplex status as a result of the quick restore operation.
If you do not do one of the above mentioned operations, the change of location of the cache
residence areas may cause I/O performance to the Cache Residency Manager for Mainframe
data to be down. For details about Cache Residency Manager for Mainframe settings, see
the HP StorageWorks XP24000/XP20000 Cache Residency Manager User's Guide.
Assessing ShadowImage for Mainframe Requirements 49