HP StorageWorks XP Remote Web Console Software - Manual (Page 34)

Table 11 Consistency Status for Split or Suspended XP Continuous Access Asynchronous S-VOLs
Description Consistency Status
(displayed at RCU)
This XP Continuous Access Asynchronous pair was probably split or suspended
alone. Update sequence consistency between this S-VOL and other S-VOLs in this Volume
consistency group is not ensured. This S-VOL cannot be used for disaster recovery
at the secondary site. This status is indicated when:
•
This pair was split by the user using the Suspend Range-LU pairsplit option.
•
This pair was suspended due to a failure that did not affect the entire consistency
group, and the Error Level pair option for this pair is set to LU.
This XP Continuous Access Asynchronous pair was split or suspended along with
the other pairs in its consistency group. Update sequence consistency between this Group
S-VOL and other S-VOLs in this consistency group is ensured. This S-VOL can be
used for disaster recovery at the secondary (remote) system (after releasing the XP
Continuous Access pair from the RCU). This status is indicated when:
•
This pair was split by the user using the Suspend Range-Group pairsplit option.
• All pairs in this consistency group were suspended due to a failure that affected
the entire consistency group (not just one pair) (for example, MCU-RCU
communications failure).
•
One pair in the group was suspended due to a failure that did not affect the
entire group, and the Error Level pair option for this pair is set to Group.
XP Continuous Access Suspend Types
Table 12 (page 35) lists and describes the XP Continuous Access suspend types, which indicate
the reason for the suspension. XP Continuous Access Synchronous pairs can only be suspended
by the MCU. XP Continuous Access Asynchronous pairs can be suspended by the MCU or by the
RCU. For further information on XP Continuous Access Asynchronous suspension conditions, see
“XP Continuous Access Asynchronous Suspension Conditions” (page 35) .
The MCU suspends an XP Continuous Access pair when it detects any of the following suspension
conditions:
•
When the MCU detects that the user has released the pair from the RCU,
•
When the MCU detects an error condition related to the RCU, the S-VOL, or an XP Continuous
Access update copy operation,
•
When the MCU is unable to communicate with the RCU, or
•
When the MCU detects an XP Continuous Access Asynchronous suspension condition.
When an XP Continuous Access Synchronous pair is suspended, 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 pair option. If a synchronous update copy operation fails, the
MCU maintains exact synchronization by reporting a unit check and decommitting the P-VOL
update, so that the host system and application program regard that write operation to the P-VOL
as failed. If the MCU accepts subsequent write I/Os for a suspended P-VOL, the MCU records the
data in the P-VOL tracks that are updated while the pair is suspended as differential data. When
a suspended XP Continuous Access Synchronous pair is resynchronized, the MCU copies the
out-of-sync P-VOL tracks to the S-VOL as differential data. XP Continuous Access does not allow
access to an S-VOL while the pair is suspended (only when split).
When an XP Continuous Access Asynchronous pair is suspended, the MCU stops performing XP
Continuous Access Asynchronous recordset operations for the pair. The MCU continues accepting
write I/Os for the suspended P-VOL and records the data in the P-VOL tracks that are updated
while the pair is suspended as differential data. The MCU and RCU also keep track of any recordsets
that were discarded during the pair suspension as differential data. When a suspended XP
34 About XP Continuous Access Operations