HP StorageWorks XP Remote Web Console Software - Manual (Page 33)

Table 9 XP Continuous Access Pair Status (continued)
S-VOL Access P-VOL Access Description Pair Status
Read only Read/write This XP Continuous Access pair consists of LUSE
volumes (for example, OPEN3*n), and an individual
LDEV within this XP Continuous Access LUSE pair has
failed due to an error condition. The status of the XP
Continuous Access LUSE volume is PAIR or COPY, and
the status of one or more LDEV pairs is PSUE or SMPL. PDUB
Pair Status for XP Continuous Access Asynchronous only:
Read only Read/write This pair is not synchronized. This pair is in transition
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. Suspending
Read only Read/write This pair is not synchronized. This pair is in transition
from PAIR, COPY, PSUS, or 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. Deleting
XP Continuous Access Split Types (PSUS)
Table 10 (page 34) lists and describes the XP Continuous Access split types. An XP Continuous
Access pair can be split by the user at any time after the initial copy operation is complete. The
user must split an XP Continuous Access pair to perform media maintenance on the P-VOL or to
access the S-VOL (S-VOL write enable).
When an XP Continuous Access Synchronous pair is split by the user, 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 options. If the P-VOL accepts write operations while the pair is split,
the MCU records the data in the P-VOL tracks that are updated as differential data. If you enabled
the S-VOL write option when you split the pair, the RCU records the data in the S-VOL tracks that
are updated while the pair is split as differential data. When the pair is resynchronized (pairresync),
the RCU sends the S-VOL differential data to the MCU, and the MCU merges the P-VOL and S-VOL
differential data to determine which tracks are out-of-sync.
When XP Continuous Access Synchronous and Asynchronous pairs exist in the same storage system,
and there are host I/Os to the XP Continuous Access Asynchronous Software pairs, if you split XP
Continuous Access Asynchronous pairs of which the P-VOL Fence Level option is Data, you must
stop the host I/Os before split operation. If you do not stop host I/Os, the pairs might be forcibly
suspended because of a timeout error, and host I/Os will be rejected.
When an XP Continuous Access Asynchronous pair is split by the user, the MCU and RCU ensure
synchronization by either completing or discarding any pending update copy operations according
to the setting of the Pending Update option. The MCU and RCU keep track of any recordsets that
were 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 XP
Continuous Access Asynchronous P-VOL, and records the data in the P-VOL tracks that are updated
while the pair is split as differential data. If you enabled the S-VOL write option when you split the
pair, the RCU also records the S-VOL tracks that are updated while the pair is split as differential
data. When the pair is resynchronized, the RCU sends the S-VOL differential data to the MCU,
and the MCU merges the P-VOL and S-VOL differential data to determine which tracks are
out-of-sync.
Pair Status 33