HP XP7 Storage - Manual (Page 150)

The swap option of the takeover command allows swapping of the primary and secondary volume
designations, so if the primary and secondary volume are switched due to a server error or package
transfer, pair operation can be continued using the reversed volumes. When control is handed
back over to the original node, swapping the volume designations again eliminates the need of
copying them. In addition, the takeover command has the option to allow the secondary volume
to be logically separated (for the purpose of recovery from a disaster at the original operating
site). The takeover command has four functions designed for HA software operation: Takeover-switch,
swap-takeover, SVOL-takeover, and PVOL-takeover. This command is not available for Business
Copy.
The Takeover-switch function
The control scripts activated by HA software are used by all nodes of a cluster in exactly the same
manner so they have no discrimination between primary and secondary pair volumes (they just
know the near and far disk in a pair). Thus, the takeover command, when activated by a control
script, must check the combination of attributes of volumes possessed by the local and remote
nodes and determine the proper takeover action. The table below shows the takeover actions.
Table 29 Near/Local and Far/Remote Volume Attributes and Takeover Actions
Takeover action Remote node Local node (Takeover node)
P-VOL status Volume attribute Fence and status Volume attribute
Reject - SMPL - SMPL
Nop-Takeover
1
- P-VOL
Unconformable - S-VOL
Reject - Unknown
Reject - SMPL Fence == Data or
Status && pair status P-VOL (primary)
Unconformable - P-VOL
== PSUE or PDUB or
MINAP == 0
PVOL-Takeover
2
- S-VOL
PVOL-Takeover
2
- Unknown
Reject - SMPL Others
Unconformable - P-VOL
Nop-Takeover
1
- S-VOL
Nop-Takeover
1
- Unknown
Nop-Takeover
1
- - Status == SSWS (After
SVOL_SSUS-takeover) S-VOL (secondary)
Unconformable - SMPL Other than SSWS
Swap-Takeover
2
PAIR or PFUL P-VOL
SVOL-Takeover
2
Others
Unconformable - S-VOL
SVOL-Takeover
2
- Unknown
Notes:
1. No action needed to allow local writes.
2. Required to allow local writes.
Nop-takeover: No operation is done to allow local writes, though the takeover command is
accepted. Personality swaps must be accomplished in another way.
150 Data replication operations with RAID Manager