HP XP7 Storage - Manual (Page 164)

Table 36 State table for Continuous Access Synchronous vs. Continuous Access Asynchronous
Transfer
data via
ESCON Writing control on Cnt Ac-S
async volume Description Disk array
internal state RAID
Manager
state
Response Writing data Continuous Access Asynchronous Continuous Access
Synchronous
None Usual Normal Same SMPL SMPL SMPL
Sidefile &
bitmap Usual* Via Sidefile Same COPY COPY COPY
Sidefile Usual Normal Deleting from COPY using [pairsplit
-S] N/A Deleting
Sidefile Usual Via Bitmap Suspending from COPY by using
[pairsplit] N/A Suspending
Sidefile Usual Via Sidefile Less than HWM Async sidefile
in use Synchronized PAIR PAIR
Sidefile Delayed Via Sidefile HWM to Threshold N/A PFUL
Sidefile Wait until
under
threshold Via Sidefile Over Threshold
Sidefile Usual Normal Deleting from PAIR using [pairsplit
-S] N/A Deleting
Sidefile Usual Via Bitmap Using [pairsplit ] Suspending
from PAIR N/A Suspending
Timeout of over
threshold
None Usual Via Bitmap Same PSUS PSUS PSUS
None Usual Via Bitmap Timeout Over Threshold None PFUS
None Usual Via Bitmap Same (link down, etc) PSUE PSUE PSUE
None Usual Via Bitmap Same PDUB PDUB PDUB
* If the host has more write I/Os in COPY state, then host write I/Os are delayed until there is enough space in the sidefile.
Legend:
Bitmap: Host write data is managed via a cylinder BITMAP of delta data.
Normal: Host write data is not managed by BITMAP or sidefile.
Usual: Host side writing response is not delayed.
HWM (High Water Mark): Sidefile quantity is over 30% of cache storage.
Continuous Access Asynchronous/Continuous Access Journal error state
In the case of an ESCON or fibre-channel (FC) failure, the S-VOL FIFO queue is missing a data
block that was transferred from the P-VOL FIFO queue. The RCU waits to store the next sequenced
data block in the S-VOL FIFO queue until the Continuous Access Asynchronous copy pending
timeout occurs (defined using Continuous Access Synchronous). In addition, the timeout value can
be specified at SVP. The default value is set to 5 minutes. If the timeout occurs during this waiting
state, the pair status changes from PAIR to PSUE, and non-sequenced data blocks are managed
by the S-VOL bitmap. The missing data block can be recovered using the pairresync command,
which merges the S-VOL bitmap with the P-VOL bitmap.
Figure 54 (page 165) shows this situation
on the secondary side.
164 Data replication operations with RAID Manager