Problems that can occur with delta resync, Setting up the 3 cnt ac-j dc cascade configuration – HP XP P9500 Storage User Manual
Page 128
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When splitting the intermediate-remote pair using flush mode, set the pair’s mirror status to
Stopped.
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When splitting the intermediate-remote pair whose S-VOL is also the delta resync S-VOL, host
I/O to the S-VOL will not be allowed even when you specify Enable for S-VOL Write in split
procedure.
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When restoring the local-intermediate pair, the intermediate-remote pair is split automatically
if its mirror status is PAIR.
•
The local-intermediate pair cannot be restored when the mirror status for the intermediate-remote
pair is COPY.
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When deleting the intermediate-remote pair:
If Mirror is specified for Range, set the mirror status for either cascade pair to Stopped.
◦
◦
If Volume is specified for Range, set the mirror status for the primary-intermediate pair to
Stopped, or set pair status to SUSPEND.
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Required pair and volume statuses for the delta resync operation:
Delta resync P-VOL and S-VOL: HOLD
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◦
Cnt Ac-J P-VOL: PAIR or PSUE
◦
Cnt Ac-J S-VOL: PAIR, PSUS, PSUE
NOTE:
The S-VOL uses two mirror IDs because of its dual use in the 3DC cascade and delta
resync configurations. The statuses shown above are required for the two mirrors as well as
for the journal in which the Cnt Ac-J pair for delta resync resides.
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Differential data is stored in the master journal but may not be completely present after a
failure. You can avoid delta resync failure by specifying that the entire P-VOL is copied to the
delta resync S-VOL in this case. See the Delta resync Failure option in
for information.
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When you delete either cascading pair, the delta resync pair is also deleted.
Problems that can occur with delta resync
Journal data will not exist, and therefore the delta resync operation will not succeed, if the following
occurs. Avoid these situations.
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After splitting the intermediate-remote pair, the S-VOL is updated.
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After the intermediate-remote pair is split and the journal volume at the intermediate site then
exceeds 70-percent as a result of updates from the primary site.
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When the delta resync P-VOL is updated and then data in the journal volume exceeds
70-percent.
The following provides solutions to other delta resync problems.
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If the delta resync S-VOL status becomes HLDE, you cannot restore it to HOLD by
resynchronizing the pair. You must delete the delta resync pair and recreate it.
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If the delta resync pair’s status does not change after the delta resync operation, check that
all requirements are fulfilled and that any problems explained in this topic have not occurred.
Check the status of the Cnt Ac-J pair and Cnt Ac-J pair for delta resync operation, and make
sure that all pairs are in the required status.
Setting up the 3 Cnt Ac-J DC cascade configuration
Set up a 3 Cnt Ac-J DC cascade configuration using the following procedure. RAID Manager is
used to set up the configuration. To set up a 3DC cascade using Cnt Ac-J and Continuous Access
Synchronous, see
“Procedure for setting up 3DC cascade ” (page 143)
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3 Cnt Ac-J data-center configurations