One-To-One Volume Copy Operations; Logical Unit (Lu) Types; Consistency Groups - HP StorageWorks XP12000 User Manual

• Cache and NVS
• Host failover software
• Duplicate volume
• Host system crash

One-to-one volume copy operations

Continuous Access XP requires a one-to-one relationship between logical volumes of volume pairs. A
volume (LU) can only be assigned to one Continuous Access XP pair at a time. Continuous Access XP
does not support operations in which one P-VOL is copied to more than one S-VOL or more than one
P-VOL is copied to one S-VOL. Because Continuous Access XP operates on logical volumes rather than
files, multivolume files require special attention. For complete duplication and recovery of a multivolume
file (such as a large database file spanning several volumes), ensure that all volumes of the file are
copied to Continuous Access XP S-VOLs, and use Continuous Access XP Asynchronous to ensure update
sequence consistency across this group of S-VOLs.

Logical unit (LU) types

Continuous Access XP supports basic LU types that can be configured on the disk array. Continuous
Access XP displays the LU type of P-VOLs and S-VOLs. A Continuous Access XP pair must consist of LUs
of the same type and capacity (for example, OPEN-3 to OPEN-3). Mainframe volumes (for example,
3390-3A/B/C, 3380-KA/B/C) cannot be assigned to Continuous Access XP pairs.
NOTE:
Contact your HP account support representative for the latest information on supported devices for
your platform.
Continuous Access XP supports the LU Size Expansion (LUSE) feature of the disk array, which configures
expanded LUs using two or more contiguous LDEVs (up to 36). If two LUSE volumes are paired with
Continuous Access XP, a LUSE P-VOL must be paired with an S-VOL of the same size and structure. For
example, if a LUSE P-VOL is connected with 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. When LUSE
volumes are assigned to a Continuous Access XP pair, the P-VOL and S-VOL must contain the same
type and number of LDEVs (for example, OPEN-3*6 to OPEN-3*6). The number of LDEV pairs in a
Continuous Access XP LUSE pair equals the number of LDEVs in each LUSE volume. When the status of all
LDEV pairs within one Continuous Access XP LUSE pair is not the same (for example, one LDEV pair is
suspended), the pair status of the Continuous Access XP LUSE pair changes to PDUB.
Continuous Access XP supports the CVS feature of the disk array, which configures custom-size LUs that
are smaller than standard-size LUs. When custom-size LUs are assigned to a Continuous Access XP pair,
the S-VOL must have the same capacity as the P-VOL.

Consistency groups

Continuous Access XP Asynchronous consistency groups have the following requirements:
• Each Continuous Access XP Async pair must be assigned to one and only one consistency group.
• Maximum number of volume pairs in one consistency group is 4,096 (entire RCU) (4,095 when
the RAID Manager command device is defined).
• Maximum number of consistency groups established for one MCU-RCU pair is 128 (00-7F).
The RCU supports a maximum of 128 groups, which includes both Continuous Access XP
Asynchronous groups and Hitachi TrueCopy Asynchronous for Mainframe (for example, 64
Continuous Access XP Asynchronous + 64 TrueCopy Asynchronous for mainframe).
• Consists of only Continuous Access XP Async pairs (no mainframe pairs).
• Only Continuous Access XP Asynchronous pairs belonging to the same CLPR can be allocated
to one Continuous Access XP consistency group. For more information about CLPRs, see the
HP StorageWorks XP Disk/Cache Partition user guide.
Continuous Access XP user guide
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