Table 2.7 Relationship Between Hitachi Truecopy Pair Status And Fence Level - Hitachi TAGMASTORE MK-90RD011-25 User Manual

Table 2.7 Relationship between Hitachi TrueCopy Pair Status and Fence Level
Hitachi TrueCopy Pair Status of Volume
Write response
Valid Valid
P
Primary volume
Secondary volume
Write response
Valid Not Valid
E
Primary volume
Secondary volume
Write response
Valid Not Valid
E
Primary volume
Secondary volume
Mirror consistency = Identity of data and sequence of data are assured via error notification
as an I/O completion.
Data consistency = Sequence of data is assured in I/O order based on host.
[1] When fence level is data: Mirroring consistency is assured, since a write error is returned
if mirror consistency with the remote SVOL is lost. The secondary volume can continue
operation, regardless of the status. Note: A PVOL write that discovers a link down situation
will, in addition to returning an error to the host, likely be recorded on [only] the PVOL side.
[2] When fence level is status: If there is a mirror consistency problem (i.e., PSUE) and it is
possible to set the SVOL to PSUE, the PVOL write completes OK. If the SVOL cannot be set to
PSUE for any reason, the PVOL write completes with an error. The mirror consistency of the
SVOL depends on its status:
PSUE: The secondary volume is dubious.
PAIR: The secondary volume can continue operation.
[3] When fence level is never: Writing to the PVOL is still enabled in the state where mirror
consistency to the SVOL is lost, regardless of whether the secondary volume status is
updated or not. Thus, the secondary could have these states:
PSUE: The secondary volume is dubious.
PAIR: The secondary volume is substantially dubious, since it can continue operation and
is also dubious. The P-VOL status must be checked to confirm the mirroring consistency.
Fence Level and Write Response
[1]
Data
OK
Mirroring
consistency
assured
P
ERROR
Mirroring
consistency
assured
E
ERROR
Mirroring
consistency
assured
P
Hitachi Command Control Interface (CCI) User and Reference Guide
[2] [3]
Status Never
OK OK
Mirroring Mirroring
consistency consistency
assured assured
OK OK
Mirroring Mirroring
consistency consistency
not assured not assured
ERROR OK
Mirroring Mirroring
consistency consistency
assured not assured
[4]
Async
OK
Data
consistency
assured
OK
Data
consistency
assured
OK
Data
consistency
assured
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