HP StorageWorks XP Remote Web Console Software - Manual (Page 51)

Logical Unit Types
XP Continuous Access supports the basic LU types that can be configured on the storage system
(for example, OPEN-3, OPEN-E, OPEN-8, OPEN-9, OPEN-L, OPEN-V). The XP Continuous Access
software displays the LU type of the P-VOLs and S-VOLs. An XP Continuous Access pair must consist
of LUs of the same type and capacity (for example, OPEN-3 to OPEN-3). Multiplatform volumes
(for example, 3390-3A/B/C) cannot be assigned to XP Continuous Access pairs. Contact your
HP Technical Support service representative for the latest information on supported devices for
your platform.
XP Continuous Access supports the LUN Expansion (LUSE) feature of the storage system, which
allows you to configure expanded LUs using two or more contiguous LDEVs (up to 36). If two LUSE
volumes are paired with XP Continuous Access, a LUSE P-VOL must be paired with an S-VOL of
the same size and the same structure. For example, if a LUSE P-VOL is connected with volumes of
1 GB, 2 GB, and 3 GB in this order, you must specify a LUSE volume that has exactly the same
size and the same connection order as the S-VOL. The number of LDEV pairs in an XP Continuous
Access LUSE pair equals the number of LDEVs in each LUSE volume. If the status of all LDEV pairs
within one XP Continuous Access LUSE pair is not the same (for example, one LDEV pair is
suspended), the pair status of the XP Continuous Access LUSE pair changes to PDUB.
XP Continuous Access also supports the CVS feature of the storage system, which allows you to
configure custom-size LUs that are smaller than standard-size LUs. When custom-size LUs are
assigned to an XP Continuous Access pair, the S-VOL must have the same capacity as the P-VOL.
Consistency Groups
The XP Continuous Access Asynchronous consistency groups have the following requirements:
•
Each XP Continuous Access Asynchronous pair must be assigned to one and only one
consistency group.
•
The maximum number of pairs in one consistency group is 8,192.
•
The maximum number of consistency groups established for one MCU-RCU pair is 128 (00-7F).
The MCU supports a maximum of 128 groups. This limit includes XP Continuous Access
synchronous groups, XP Continuous Access asynchronous groups, and TrueCopy Asynchronous
for Mainframe groups (for example, 32 XP Continuous Access synchronous + 32 XP Continuous
Access asynchronous + 64 TrueCopy Asynchronous for Mainframe).
•
If the XP Continuous Access pairs are synchronous, the XP Continuous Access synchronous
pairs can be intermixed in a consistency group.
•
If the XP Continuous Access pairs are asynchronous, the XP Continuous Access pairs and
TrueCopy for Mainframe pairs cannot be intermixed in a consistency group.
•
If you specify a consistency group for XP Continuous Access Asynchronous pairs, only XP
Continuous Access asynchronous pairs that belong to the same CLPR can be allocated to one
XP Continuous Access asynchronous consistency group. For further information on CLPRs, see
the HP XP24000/XP20000 Disk/Cache Partition User Guide.
Accessing XP Continuous Access P-VOLs and S-VOLs
To ensure maximum data integrity during normal XP Continuous Access operations, the RCU rejects
all write operations issued by a host to an XP Continuous Access S-VOL. If you need write access
to an XP Continuous Access S-VOL, you must split the pair using the S-VOL write option (see
“S-VOL
Write Option” (page 19) ). When you resynchronize (resync) the split pair, the RCUsends the S-VOL
differential data to the MCU to ensure proper resynchronization of the pair.
Cache and NVS
Cache and nonvolatile storage (NVS) must be operable for both the MCU and RCU of an XP
Continuous Access pair. If not, the XP Continuous Access paircreate operation will fail. The remote
Requirements and Restrictions for Using XP Continuous Access 51