Accessing truecopy m-vols and r-vols, Cache, nvs, and dasd fast write, Consistency groups – HP StorageWorks XP Remote Web Console Software User Manual
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TrueCopy for the XP128/XP1024/XP10000/XP12000
NOTE:
The host I/O time-stamping function is not supported by 3380 LVIs. If you plan to use TC390A
pairs, the TC390A M-VOLs and R-VOLs must be 3390 LVIs.
In the case that M-VOL or R-VOL is 3390-L LVI under the connection of the disk array, and the number of
cylinders is more than 10,017, the capacity of the M-VOL and R-VOL must be the same.
CAUTION:
If you use TC390 to copy from a smaller volume to a larger volume, you will not be able to
perform TC390 operations in the reverse direction (from the secondary site to the primary site) after a
disaster has occurred and the secondary site was used for production. This restriction exists because
TC390 does not support copying from a larger volume to a smaller volume. HP strongly recommends that
this capability (copying from a smaller volume to a larger volume) only be used for data migration
purposes.
CAUTION:
If you use a Fujitsu operating system, and utilize TC390A to copy from a smaller capacity of
M-VOL to the larger capacity of R-VOL, an error will occur when the write operation will be performed to
the former R-VOL after the pair has been deleted. If the write operation is required on this volume, make the
capacity of M-VOL and R-VOL same, and then create a pair.
Accessing TrueCopy M-VOLs and R-VOLs
Write operations to a TC390 M-VOL that specify normal authorization are duplicated on the R-VOL of the
TC390 pair. Write operations with diagnostic or device support authorization, such as ICKDSF, are
completed at the M-VOL but are not duplicated at the R-VOL. Therefore, you must suspend a TC390 volume
pair before performing ICKDSF media maintenance on the M-VOL. For instructions on running ICKDSF on
TC390 volumes, see ”
ICKDSF Considerations for TrueCopy Volumes
To ensure maximum data integrity during normal TC390 operations, the RCU rejects all read and write
operations issued by a host to a TC390 R-VOL. If you need read-only access to a TC390 R-VOL, you must
have the R-VOL read option (see ”
” on page 28) enabled on the RCU and you must
suspend the pair to read the R-VOL. The R-VOL read option can be enabled by the HP representative only.
If you need write access to a TC390 R-VOL (for example, to perform ICKDSF), you must delete the pair from
the RCU to change the R-VOL pair status to simplex. For instructions on running ICKDSF on TC390 volumes,
see ”
ICKDSF Considerations for TrueCopy Volumes
Cache, NVS, and DASD Fast Write
Cache and nonvolatile storage (NVS) must be operable for both the MCU and RCU of a TC390 volume
pair. If not, the Add Pair operation will fail. The remote disk array cache should be configured to
adequately support the TC390 remote copy workloads as well as any local workload activity.
DASD fast write (DFW) is required at the MCU and RCU only when the DFW-to-R-VOL required TC390
pair option (see ”
Creating TrueCopy Volume Pairs (Add Pair)
” on page 115) is specified. If DFW to an
R-VOL is blocked and the TC390 pair was established with the DFW-to-R-VOL required pair option, the
MCU detects DFW OFF at the R-VOL and suspends the pair. TC390 pairs that were established using PPRC
commands use the default value of not required and therefore are not suspended when DFW to the R-VOL
is blocked.
NOTE:
The DFW to R-VOL setting does not affect the I/O performance of the M-VOLs. If one side of
cache is closed due to an RCU failure, the TC390 copy operation still uses DFW. The only difference
between not required and required is that new pairs cannot be established with the DFW-to-R-VOL
required option when one side of RCU cache is closed (the add pair operation fails).
Consistency Groups
The TC390A consistency groups have the following requirements: