HP StorageWorks XP24000 Continuous Access Software User and Reference Guide, v01 (T5278-96002, June 2007)

Note: You mustoperate theRemoteWeb Console software inmodifymodetoperform Continuous
Access operations. Users in view mode can only view Continuous Access information.
• About th e license of Continuous Access Asynchronous:
To use Continuous Access Asynchronous, you must install not only Continuous Access
Asynchronous but also Continuous Access. So, you need license codes for both Continuous
Access Asynchronous and Continuous Access. Also, the license capacity of Continuous Access
and the license capacity of Continuous Access Asynchronous must satisfy the following equation:
License capacity of Continuous Access ≥ License capacity of Continuous Access Asynchronous
Requirements
and
Restrictions for Using Continuous Access
Continuous Ac
cess has the following requirements and restrictions:
• One-to-one volume copy operations
• Logical unit (LU) type (also called device emulation or type)
• Consistency
groups
• Accessing Continuous Access P -VOLs and S-VOLs
• Cache and NVS
• Host failov
er
software
• Duplicate volume
• Host system crash
One-to-One Volume Copy Operations
Continuous Access requires a one-to-one relationship between the volumes of the pairs. A volume (LU)
can only be assigned to one Continuous Access pair at a time. 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. B ecause Continuous Access operates on volumes rather than on files, multivolume files
require special attention. For complete duplication and recovery of a multivolume file (for example, a
large database file which spans several volumes), make sure that all volumes of the file are copied
to
Continuous Access S-VOLs, and use Continuous Access Asynchronous to ensure update sequence
consistency across this group of S-VOLs.
Logical Unit (LU) T ypes
Continuous Access supports the basic LU types which can be configured on the storage system (for
example, O PEN-3, OPEN-E, OPEN-8, OPEN-9, OPEN-L, O PEN-V). The Continuous Access software
display
s
the LU type of the P-VOLs and S-VOLs. A 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 Continuous Access pairs.
Note: Please contact your HP service
representative for the latest information on supported devices for your platform.
Contin
uous Access suppor ts the LUN Expansion (LUSE) feature of the storage system, which allows you
to
confi
gure expanded LUs using t wo or more contiguous LDEVs (up to 36). If two LUSE volumes are
paire
d
with ContinuousAccess,a LUSE P-VOLmustbepairedwithan S-VOL of thesame sizeand the
same structure. Forexample,ifaLUSE P-VOLisconnected with volumesof1GB,2GB,and 3GBin
this order, youmustspecify aLUSEvolumewhich hasexactly thesamesize and thesameconnection
order
as the
S-VOL. The number of LDEV pairs in a Continuous Access LUSE pair equals the number
of
LDEVs in each LUSE volume. If the status of all LDEV pairs within one Continuous Access LUSE pair
is not
the same (for example, one LDEV pair is suspended), the pair status of the Continuous Access
LUSE
pair changes to PDUB.
Cont
inuous Access also supports the Virtual LVI/LUN feature of the storage system, which allows you to
confi
gure custom-size LUs which are sma ller than standard-size LUs. When custom-size LUs are assigned
to a
Continuous Access pair, the S-VOL must have the same capacity as the P-VOL.
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Preparing for Continuous Access Operations