HP XP Business Copy Software - Manual (Page 13)

Business Copy XP user guide for the XP128/XP1024 13
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 ” on
page 16.
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.
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 ” on page 25 for further information on the cascade function.
BC software on the Command View XP management station or XP Remote Web Console
When installed on the Command View XP management station or XP Remote Web Console, the BC
software displays BC information and performs BC operations. For Command View XP, the management
station can be attached to multiple disk arrays. The Command View XP management station or XP Remote
Web Console acquires status from and issues commands to BC P-VOLs and S-VOLs.
BC requirements
BC operations provide disk array-internal copies of UNIX/PC server volumes (LUs) on the disk array.
Table 3 describes operational requirements for the use of BC.
Table 3 BC operational requirements
Parameter Requirement
Pair objects Logical devices (LDEVs): OPEN-x (such as OPEN-3, OPEN-9, OPEN-E, or OPEN-V),
including CVS and LUSE volumes. Devices must be installed and configured. The
P-VOL and S-VOL must be the same type (for example, OPEN-3 to OPEN-3 is
allowed, OPEN-3 to OPEN-9 is not allowed).
A custom-size P-VOL must be paired with S-VOLs of the same type and capacity. A
LUSE P-VOL must be paired with S-VOLs of the same size and structure. For example,
if a LUSE P-VOL is connected to volumes of 1GB, 2GB, and 3GB in this order, you
must specify the LUSE volume that has exactly the same size and connection order as
the S-VOL.
BC does not support multiplatform devices (for example, 3390-3A, -3B, or -3C).
Volumes that form a Flex Copy XP pair cannot be specified as P-VOLs or S-VOLs.
Number of copies Maximum of three copies (S-VOLs) per primary volume (P-VOL). Maximum of one
P-VOL per S-VOL (P-VOLs cannot share an S-VOL).
An additional six copies can be created by using the BC cascade function.
Maximum number of pairs 1 The total number of BC, ShadowImage (SI390), ShadowImage - FlashCopy®, Auto
LUN XP, and Flex Copy XP (or Flex Copy XP V2) volume pairs. For more information,
see ” Maximum number of pairs” on page 14 .
Maximum number of
S-VOLs
4,095