HP StorageWorks Continuous Access XP user guide for the XP10000/XP12000 (December 2005)

Continuous Access XP user guide for the XP10000/XP12000 27
Continuous Access XP split types (PSUS)
Table 6 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.
Pair Status for Continuous Access XP LUSE volumes only:
PDUB Continuous Access XP pair consists of LUSE
volumes (for example, OPEN3*n), and an
individual LDEV within this
Continuous
Access XP
LUSE pair failed due to some error
condition. The status of the Continuous
Access XP
LUSE volume is PAIR or COPY,
and the status of one or more LDEV pairs is
PSUE or SMPL.
Read/write Read only
Pair Status for Continuous Access XP Asynchronous only:
Suspending 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.
Read/write Read only
Deleting 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.
Read/write Read only
Table 5 Continuous Access XP Asynchronous pair status descriptions (continued)
Pair status Description P-VOL access S-VOL access