One-to-one volume copy operations, Logical unit (lu) types, Consistency groups – HP StorageWorks XP Remote Web Console Software User Manual
Page 32
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“Accessing XP Continuous Access P-VOLs and S-VOLs” (page 33)
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“Cache and nonvolatile storage (NVS)” (page 33)
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“Host failover software” (page 33)
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One-to-one volume copy operations
XP Continuous Access requires a one-to-one relationship between logical volumes of volume pairs.
A volume (LU) can only be assigned to one XP Continuous Access pair at a time. XP Continuous
Access 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 XP Continuous Access 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 XP Continuous Access S-VOLs, and use XP Continuous Access
Asynchronous to ensure update sequence consistency across this group of S-VOLs.
Logical unit (LU) types
XP Continuous Access supports basic LU types that can be configured on the disk array. XP
Continuous Access displays the LU type of 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). Mainframe volumes
(for example, 3390-3A/B/C, 3380-KA/B/C) cannot be assigned to XP Continuous Access pairs.
NOTE:
Contact your HP account support representative for the latest information on supported
devices for your platform.
XP Continuous Access 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 XP Continuous Access, 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 an XP Continuous Access 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 an XP Continuous Access LUSE pair equals the number of LDEVs in
each LUSE volume. When 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 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 an XP Continuous
Access pair, the S-VOL must have the same capacity as the P-VOL.
Consistency groups
XP Continuous Access consistency groups have the following requirements:
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Each XP Continuous Access pair must be assigned to one and only one consistency group.
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Maximum number of volume pairs in one consistency group is 4,096.
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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 Hitachi TrueCopy
asynchronous for Mainframe (for example, 32 XP Continuous Access Synchronous + 32 XP
Continuous Access Asynchronous + 32 Hitachi TrueCopy Asynchronous for z/OS).
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Synchronous pairs and asynchronous pairs cannot be intermixed in a consistency group.
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Preparing for XP Continuous Access operations