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

Point-in-Time (
P iT) Data Duplication Using Continuous Access As y nchronous
Continuous Acc
ess Asynchronous enables you to make Point-in-Time (PiT) duplicates of groups of volumes.
The Continuous Access A synchronous Group and Drain pairsplit options can be used together to create a
PiT copy, relative to an application, of an entire Continuous Access Asynchronous consistency group of
volumes. To produce a PiT duplicate of an existing Continuous Access Asynchronous consistency group:
1. Stop all host updates to all Continuous AccessAsynchronousP-VOLsinthe group.
2. After all P-VOL updates have c ompleted, split the Continuous Access Asynchronous group using
the
Group and Drain pairsplit options. If you are splitting the group at the main site, issue the
pairsplit-r/group command to one P-VOL in the MCU. If you are splitting the group at the remote
site, issue the pairsplit-r/group command to one S-VOL in the RCU.
Note: The copy pending timeout setting for the group determines the maximum amount of time
that the
pairsplit-r/drain operation can take (see description of Drain above).
3. When the st
atus of all
Continuous Access Asynchronous pairs in the group has changed to
PSUS,the d
uplicate set of volumes is complete. If desired, you can restart the application
at the
main site.
Po wering Off/On Continuous Access Components
The user is responsible for controlling power-off activities for storage systems involved in Continuous
Access operations. If you need to power off the storage system, call your HP service representative or
HP
technical support for assistance. The following sections provide instructions for performing planned
outages of Continuous Access components.
If power is removed from an MCU while Continuous Access operations are in progress, the Continuous
Access p airs are not a ffected, but the update sequence consistency of the Continuous Access
Asynchronous groups at theRCU maybeaffected(see“Planned Outage of the MCU ” on page 124
for further information). When power is restored to an MCU, the MCU communicates with its RCU(s)
to
confirm the pair status of the S-VOLs. M ake s ure tha t Continuous Access communications are fully
restored (all paths have normal status) before beginning I/O operations to the P-VOLs. If the MCU
accepts a write I/O operation for a P-VOL before this confirmation is complete, the MCU will suspend
the pair
and change the status of the P-VOL to suspended-by RCU (the MCU will not be able to change
the pair
status of the S-VOL).
If power is removed from an RCU or remote copy connection while Continuous Access operations are in
progress, the MCU(s) will detect the communications failure, suspend all affected pairs, and generate
SIMs reporting the failures. The MCU will change the status of the P-VOLs to suspended-by RCU but will
notbeabletochangethe status of theS-VOLs.
Note: If an MCU/RCU is powered off and its backup batteries are fully discharged while Continuous
Access pairs are suspended, the P-VOL/S-VOL differential data will not be retained. In this unlikely
case, the MCU/RCU will mark all tracks of all suspended Continuous Access P-VOLs as modified,
so that the
MCU will perform the equivalent of an entire initial copy operation when the pairs are
resynchronized. (The S-VOL differential data is used for Continuous Access A synchronous operations and
for the Continuous Access S-VOL write enable o ption.)
Pl
anned
Outage of the MCU
Ap
lanned MCU outage does not affect Continuous Access Synchronous. For Continuous Access
Asynchronous operations, the MCU must communicate with the RCU even when there are no P-VOL
update
I/Os from the primary system. During the power-off sequence, the MCU will automatically
s
uspend all Continuous Access Asynchronous pairs in the PAIR and COPY states (suspend type =
MCU
P/S-OFF). During the power-on-reset sequence, the MCU will automatically resynchro nize these
suspended pairs (pairs with other suspend t ypes are not automatically resynchronized).
124
Performing Continuous Access Pair Operations