Continuous Access Xp Split Types (Psus) - HP StorageWorks XP12000 User Manual

Pair status
Pair Status for Continuous Access XP Asynchronous only:
Suspending
Deleting

Continuous Access XP split types (PSUS)

Table 8 describes Continuous Access XP split types. You can split a Continuous Access XP pair at any
time after the initial copy operation is complete. You must split a Continuous Access XP pair to perform
media maintenance on the P-VOL or change the S-VOL (S-VOL write enable).
When you split a Continuous Access XP Synchronous pair, the MCU ensures synchronization by
completing any pending update copy operation before changing the status to PSUS. After the pair status
changes to PSUS, the MCU stops performing update copy operations to the S-VOL and may or may not
continue accepting write I/Os for the P-VOL, depending on the P-VOL fence level and pairsplit-r options.
If the P-VOL accepts write operations while the pair is split, the MCU tracks P-VOL cylinders updated. If
you enabled the S-VOL write option when you split the pair, the RCU tracks S-VOL cylinders updated while
the pair is split. When the pair is resumed (pairresync), the RCU sends the S-VOL cylinder bitmap to the
MCU, and the MCU merges the P-VOL and S-VOL bitmaps to determine which cylinders are out-of-sync.
When you split a Continuous Access XP Asynchronous pair, the MCU and RCU ensure synchronization by
completing or discarding pending update copy operations according to the user-specified drain/purge
pairsplit option. The MCU and RCU track recordsets discarded during the pairsplit operation. After the
pair status changes to PSUS, the MCU stops performing recordset operations for the pair, continues
accepting write I/Os for the split Continuous Access XP Async P-VOL, and tracks P-VOL cylinders updated
while the pair is split. If you enabled the S-VOL write option when you split the pair, the RCU also tracks
the S-VOL cylinders updated while the pair is split. When the pair is resumed, the RCU sends the
S-VOL cylinder bitmap to the MCU, and the MCU merges the P-VOL and S-VOL bitmaps to determine
which cylinders are out-of-sync.
A split (or suspended) Continuous Access XP Async S-VOL has an additional status called consistency
status. The consistency status is displayed only at the RCU and indicates the S-VOL's update sequence
consistency with respect to other S-VOLs in the same group.
30
Continuous Access XP for the Array
Description
Pair is not synchronized. This pair is
transitioning from PAIR or COPY to
PSUS/PSUE. When the split/suspend pair
operation is requested, the status of all
affected pairs changes to Suspending.
When the split/suspend operation
is complete, the status changes to
PSUS/PSUE.
Pair is not synchronized. This pair
is transitioning from PAIR, COPY, or
PSUS/PSUE to SMPL. When the pairsplit-S
operation is requested, the status of all
affected pairs changes to Deleting. When
the pairsplit-S operation is complete, the
status changes to SMPL.
P-VOL access S-VOL access
Read/write Read only
Read only
Read/write