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.
