HP XP Business Copy Software - Manual (Page 13)

Requirement Parameter
A maximum of 8,192 pairs (8,192 P-VOLs and 8,192 S-VOLs) can be created per
disk array.
NOTE:
The maximum number of pairs equals the total number of BC, Snapshot XP,
ShadowImage for z/OS, Hitachi FlashCopy Mirroring, Hitachi FlashCopy
Mirroring Version 2, Auto LUN XP, and Flex Copy XP volume pairs.
When you use RAID Manager, the command device reduces the maximum number
of BC pairs to 8,191 (8,191 P-VOLs and 8,191 S-VOLs) when configuring pairs in
a ratio of 1 S-VOL to 1 P-VOL.
If some BC pairs contain LUSE volumes, or if an application other than BC is used,
the maximum number of BC pairs might be less than 8,192 (or 8,191).
See
Maximum number of pairs for the array for information about calculating the
maximum number of BC pairs.
Maximum number of
pairs
1
8,192 (8,191 if RAID Manager is used).
Maximum number of
S-VOLs
L1 pairs = 0, 1, and 2 (a total of 3 pairs)
L2 pairs =1 and 2 (a total of 2 pairs)
MU (mirror unit) num-
bers of cascade pairs
All combinations supported: RAID1-RAID1, RAID5-RAID5, RAID6-RAID6, RAID1-RAID5,
RAID1-RAID6, RAID5-RAID1, RAID5-RAID6, RAID6-RAID1, RAID6-RAID5.
Combinations of RAID
levels (primary- sec-
ondary)
If a failure occurs requiring the disk array to utilize dynamic sparing or automatic
correction copy, the status of the paired volumes associated with the failed physical
device is not affected. Dynamic sparing and
automatic correction
copy
Maintenance of a PDEV that is not used by BC does not affect BC operations or the
status of BC pairs. If a PDEV contains LDEVs used by BC, you can maintain that PDEV
independently of the BC operations and pair status.
Physical device
(PDEV) maintenance
If the status of a BC pair is COPY(PD), PAIR, PSUS, PSUS(SP), COPY(SP), COPY(RS),
or COPY(RS-R), maintenance for the LDEVs used by that pair is restricted. Maintenance
is also restricted for LDEVs with the Reserve attribute.
To maintain these LDEVs, suspend or delete the BC pair, or reset (unreserve) the
Reserve attribute.
Logical device (LDEV)
maintenance
If disk array cache maintenance is performed during a period of high I/O usage, one
or more BC pairs may be suspended. Reduce the I/O load before cache maintenance.
Cache maintenance
For pairs in PAIR status, host I/Os are copied to S-VOLs asynchronously. To synchronize
a pair and access the S-VOL as soon as possible, take the P-VOL offline and split the
pair before using the S-VOL. If the P-VOL cannot be taken offline, a P.I.T. backup still
occurs if a pairsplit is issued. When all data on the P-VOL (up to the pairsplit time) is
copied to the S-VOL, the pair is split and the S-VOL becomes available for use (R/W).
The operation may take longer to complete if high write activity from the host to the
P-VOL is occurring. A P.I.T. backup can also be performed by issuing a pairsplit to P-
VOLs in the SMPL (simplex) state (in this case the pairsplit operation simultaneously
creates and splits new BC pairs.).
Point-in-time backup
When a failure of any kind prevents a BC copy operation from completing, the disk
array suspends the pair. If an LDEV failure occurs, the disk array suspends the pair.
If a PDEV failure occurs, BC pair status is not affected because of the RAID architecture,
but copy pace may be degraded.
Failures
XP Business Copy User Guide 13