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differential data in the P-VOL (due to P-VOL and S-VOL updates) is copied to the S-VOL, so the S-VOL is
again identical to the P-VOL. For reverse resync, the differential data in the S-VOL (due to P-VOL and
S-VOL updates) is copied to the P-VOL, so the P-VOL is now identical to the S-VOL.
NOTE:
BC S-VOLs are updated asynchronously. For a volume pair with PAIR status, the P-VOL and S-VOL may
not be identical. For further information on BC update copy operations, see Paircreate operation.
BC P-VOLs or S-VOLs should not be concentrated in the same RAID group. To disperse workloads of
RAID groups, each RAID group should have both P-VOLs and S-VOLs evenly distributed. BC pairs for
which BC operations are performed simultaneously should be in different RAID groups. If BC pairs are
concentrated in only a few RAID groups, host I/O performance may be degraded.
If the disk array is overloaded, increase cache, disk adapters, and/or RAID groups. Consider assigning
BC S-VOLs in newly installed RAID groups. If you continue BC operations with an overloaded disk
array, host I/O performance may be degraded.
Copy Threshold option
If BC performs copy operations when the disk array workload is heavy, host server I/O performance
might be degraded. To minimize this performance degradation, enable Copy Threshold,which
temporarily stops all BC copy operations when the disk array has a heavy workload. Copy operations
that are stopped by the Copy Threshold option resume when the disk array workload is lighter.
This option is different from the Host I/O Performance option (Host I/O Performance option), because it is
effective only when the disk array workload is heavy.
NOTE:
Contact your HP support account representative for more information about the Copy Threshold option.
In addition to BC operations, Copy Threshold temporarily stops copy operations for the following
applications when the disk array workload is heavy:
• Auto LUN XP
• ShadowImage for z/OS
• Hitachi FlashCopy Mirroring
• Hitachi FlashCopy Mirroring Version 2
• Snapshot XP
• Flex Copy XP
Cascade pairs
The BC cascade function adds a second layer of pairs onto the first layer of original BC pairs. Use these
two layers of pairs (L1 and L2) to create and maintain up to nine copies of one original BC primary
volume (P-VOL). See Cascade function for further information on the cascade function.
BC software on the Command View XP management station
When installed on the Command View XP management station, the BC software displays BC information
and performs BC operations. The Command View XP management station can be attached to multiple
disk arrays. The Command View XP management station acquires status from and issues commands to
BC P-VOLs and S-VOLs.
BC re
quirements for the array
BC operations provide local copies of UNIX/PC server volumes (LUs) on the disk array. The following
table describes the operational requirements for BC.
Business Copy XP user guide
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