HP XP Racks - Manual (Page 72)

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Managing power-off for systems and network devices
Though you are responsible for controlling power-off activities, it is advisable to check with your
HP representative for assistance.
The following topics provide information for planned outages when Continuous Access Synchronous
is present.
General information
Please review the following system behaviors regarding powering off:
•
Cnt Ac-S pairs are not affected when power is removed from a primary system while operations
are in progress.
•
When power is restored on the primary system, the system communicates with the secondary
systems to confirm S-VOL pair status(es). Make sure that Cnt Ac-S communications are fully
restored (all paths have normal status) before beginning I/O operations to the P-VOL.
If the primary system accepts an I/O for a P-VOL before this, all communications are restored,
and the primary system splits the pair and changes P-VOL status to PSUE-by Remote Storage
System. The primary system cannot change the pair status of the S-VOL.
•
If power is removed from a secondary system or from a data path component while Cnt Ac-S
operations are in progress, the primary system detects the communication failure, splits all
affected pairs, and generates SIMs reporting the failures. The primary system changes the
P-VOL status to PSUE-by Remote Storage System but cannot change the status of the S-VOLs.
•
If a primary is powered off and the backup batteries are fully discharged while pairs are split,
differential data is retained to SSD. In this unlikely case, MCU copies differential data to RCU
when the pairs are resynchronized.
Planned outage of the primary system
A planned outage of the primary system does not affect Continuous Access Synchronous.
Planned outage of the secondary system or remote path
You must split the pairs in a secondary system prior to a planned outage of the system or to a data
path component (for example, switch, channel extender).
72 Monitoring and maintaining the Cnt Ac-S system