Hitachi HUS VM, User And Reference Manual

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• If you attempt to read non-reflected data on S-VOL in PVOL_PSUS &
SVOL_COPY state, then ShadowImage copies non-reflected data from P-
VOL to S-VOL, and returns the correct data after copied. This will bring
the performance degradation (1/6 to 1/15 with IOPS) to read on the S-
VOL.
• If you attempt to write non-reflected data on S-VOL in PVOL_PSUS &
SVOL_COPY state, then ShadowImage copies non-reflected data from P-
VOL to S-VOL, and writing data is managed as delta data for S-VOL after
copied. This will bring the performance degradation(1/6 to 1/8 with IOPS)
to write on the S-VOL.
• If you attempt to write to the data on P-VOL that does not still reflected
the data to S-VOL, then ShadowImage copies non-reflected data from P-
VOL to S-VOL, and writing data is managed as delta data for P-VOL. This
will bring the performance degradation(1/6 to 1/8 with IOPS) to write on
the P-VOL.
• The state changes for pairsplit are (WD = Write Disable, WE = Write
Enable):
If P-VOL has non-reflected data in PAIR state:
Behavior of OLD pairsplit at T0
T0: PVOL_PAIR from/to SVOL_PAIR(WD)
T1: PVOL_COPY from/to SVOL_COPY(WD)
T2: PVOL_PSUS from/to SVOL_SSUS(WE)
Behavior of first pairsplit at T0
PVOL_PAIR from/to SVOL_PAIR(WD)
PVOL_PSUS from/to SVOL_COPY(WE)
PVOL_PSUS from/to SVOL_SSUS(WE)
If P-VOL has been reflected all data to S-VOL in PAIR state:
Behavior of OLD pairsplit at T0
T0: PVOL_PAIR from/to SVOL_PAIR(WD)
T1: PVOL_PSUS from/to SVOL_SSUS(WE)
Behavior of First pairsplit at T0
PVOL_PAIR from/to SVOL_PAIR(WD)
PVOL_PSUS from/to SVOL_SSUS(WE)
• The state changes for paircreate -split are:
Behavior of OLD paircreate -split at T0
T0: SMPL from/to SMPL
T1: PVOL_COPY from/to SVOL_COPY(WD)
T2: PVOL_PSUS from/to SVOL_SSUS(WE)
Behavior of First paircreate -split at T0
SMPL from/to SMPL
PVOL_PSUS from/to SVOL_COPY(WE)
PVOL_PSUS from/to SVOL_SSUS(WE)
• If you 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 P-VOL is already in PVOL_PSUS state. If you
want to wait the "SVOL_SSUS" state, and then you must check the status
of the S-VOL becomes "SVOL_PSUS" via the return code using
pairvolchk -ss command on S-VOL side or pairvolchk -ss -c command
on P-VOL side. Or you can use pairevtwait -ss ssus on both P-VOL and
S-VOL, pairevtwait -ss ssus -l on S-VOL locally.
• If you attempt the pairresync -restore or pairsplit -S in PVOL_PSUS &
SVOL_COPY state, then ShadowImage will reject this command due to
Data replication operations with CCI
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Command Control Interface User and Reference Guide