HP XP RAID Manager Software - Manual (Page 137)

NOTE: If the P-VOL does not have Write in the PAIR state, then data identical with an S-VOL is
guaranteed. Therefore, when using the S-VOL with the SMPL state, after stopping Write to the
P-VOL, generate a paired volume, and then split the paired volume after confirming that the paired
volume has the PAIR status. In the PSUE state, Business Copy does not manage differential data at
the P-VOL or S-VOL. Therefore, pairresync issued to a pair in the PSUE state is all copy performance,
but the copy progress rate returned by the -fc option of the pairdisplay command indicates “0%”.
[1]: The state change (2 to 4) is effective for only the COPY state that is changed without
specification of -split for paircreate command.
[2]: The (2 to 4) state change appears as P-VOL_PSUS & S-VOL_COPY (see example below), and
reading and writing are enabled for S-VOL in S-VOL_COPY state.
# pairsplit -g oradb
# pairdisplay -g oradb -fc
Group PairVol(L/R) (Port#,TID,LU-M), Seq#, LDEV#.P/S, Status, % , P-LDEV# M
oradb oradev3(L) (CL2-N , 3, 4-0) 8071 28..P-VOL PSUS, 100 29 W
oradb oradev3(R) (CL2-N , 3, 5-0) 8071 29..S-VOL COPY, 97 28 -
P-VOL_PSUS & S-VOL_COPY is the non-reflected PSUS state that data is still being copied from the
P-VOL to the S-VOL, and this state has the following specific behavior.
•
If you attempt to read non-reflected data on S-VOL in P-VOL_PSUS & S-VOL_COPY state, then
Business Copy 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 P-VOL_PSUS & S-VOL_COPY state, then
Business Copy 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
Business Copy 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 first pairsplit at T0 Behavior of OLD pairsplit at T0
P-VOL_PAIR from/to S-VOL_PAIR(WD) T0 P-VOL_PAIR from/to S-VOL_PAIR(WD)
P-VOL_PSUS from/to S-VOL_COPY(WE) T1: P-VOL_COPY from/to S-VOL_COPY(WD)
P-VOL_PSUS from/to S-VOL_SSUS(WE) T2: P-VOL_PSUS from/to S-VOL_SSUS(WE)
If P-VOL has been reflected all data to S-VOL in PAIR state:
Behavior of First pairsplit at T0 Behavior of OLD pairsplit at T0
P-VOL_PAIR from/to S-VOL_PAIR(WD) T0: P-VOL_PAIR from/to S-VOL_PAIR(WD)
P-VOL_PSUS from/to S-VOL_SSUS(WE) T1: P-VOL_PSUS from/to S-VOL_SSUS(WE)
•
The state changes for paircreate -split are:
Behavior of First paircreate -split at T0 Behavior of OLD paircreate -split at T0
SMPL from/to SMPL T0: SMPL from/to SMPL
P-VOL_PSUS from/to S-VOL_COPY(WE) T1: P-VOL_COPY from/to S-VOL_COPY(WD)
Continuous Access Synchronous, Business Copy, and Continuous Access Journal operations 137