22
Chapter 2 Overview of CCI Operations
– The state changes for pairsplit are (WD = Write Disable, WE = Write Enable):
If PVOL has non-reflected data in PAIR state:
Behavior of OLD pairsplit at T0
Behavior of First pairsplit at T0
T0 PVOL_PAIR
ÅÆ
SVOL_PAIR(WD)
PVOL_PAIR
ÅÆ
SVOL_PAIR(WD)
T1: PVOL_COPY
ÅÆ
SVOL_COPY(WD)
PVOL_PSUS
ÅÆ
SVOL_COPY(WE)
T2: PVOL_PSUS
ÅÆ
SVOL_SSUS(WE)
PVOL_PSUS
ÅÆ
SVOL_SSUS(WE)
If PVOL has been reflected all data to SVOL in PAIR state:
Behavior of OLD pairsplit at T0
Behavior of First pairsplit at T0
T0: PVOL_PAIR
ÅÆ
SVOL_PAIR(WD)
PVOL_PAIR
ÅÆ
SVOL_PAIR(WD)
T1: PVOL_PSUS
ÅÆ
SVOL_SSUS(WE)
PVOL_PSUS
ÅÆ
SVOL_SSUS(WE)
– The state changes for paircreate -split are:
Behavior of OLD paircreate -split at T0
Behavior of First paircreate -split at T0
T0: SMPL
ÅÆ
SMPL
SMPL
ÅÆ
SMPL
T1: PVOL_COPY
ÅÆ
SVOL_COPY(WD)
PVOL_PSUS
ÅÆ
SVOL_COPY(WE)
T2: PVOL_PSUS
ÅÆ
SVOL_SSUS(WE)
PVOL_PSUS
ÅÆ
SVOL_SSUS(WE)
– If you will attempt the
“
pairevtwait -s psus
”
in PVOL_PSUS & SVOL_COPY state, then pairevtwait will return immediately
even if the S-VOL is still in SVOL_COPY state because PVOL is already in PVOL_PSUS state. If you want to wait the
“
SVOL_SSUS
”
state, and then you must check the status of the SVol becomes “SVOL_PSUS” via the return code used
“pairvolchk -ss” command on SVOL side or “pairvolchk -ss -c” command on PVOL side.
OR you can use “pairevtwait -ss ssus” on both PVOL and SVOL, “pairevtwait -ss ssus -l” on SVOL locally.
– If you will attempt the
“
pairresync -restore
”
or
“
pairsplit -S
”
in PVOL_PSUS & SVOL_COPY state, then HOMRCF will
reject this command due to unable to perform. In this case, you need to wait until the SVol state becomes
“
SVOL_SSUS
”
.
Table 2.4
Pair Status versus SnapShot Commands
Copy-on-Write Snapshot Command
Paircreate
Pairsplit
Pairresync
Pair Status No -split
-split
-E option
-C option
-S option
Resync
c
SMPL Accepted
d
Rejected
Rejected
Rejected Acceptable Rejected
d
COPY
RCPY
Acceptable
Rejected
Rejected
Rejected
Rejected Acceptable
e
PAIR
Acceptable
Accepted*
f
Rejected Accepted
f
Accepted
c
Acceptable
f
PSUS
(PFUS)
Rejected Acceptable
Rejected Acceptable
Accepted
c
Accepted*
d
g
PSUE Rejected
Rejected Acceptable Rejected Accepted
c
Accepted*
d
Accepted*
: Accepted*: A command is accepted and issued; whether this command is
executed or not depends on the microcode version of the RAID storage system.
Notes:
Pairsplit (“simplex -S”) of SnapShot volume will be returned without verification of state
transition that waits until SMPL state.
In SMPL state, the volume which was SVOL
becomes R/W disable and data is discarded.
In the “PSUE” state, SnapShot does not manage for differential data between the
primary volume and secondary volume.
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