EMC VMAX 100K, Product Manual

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Table 43 R2 device accessibility
Host interface state SRDF R2 state Accessibility
Write Enabled (Read/ Write) Ready Read/Write
Not Ready Read/Write
Write Disabled (Read Only) Ready Read Only
Not Ready Read Only
Not Ready Any Unavailable
Dynamic device personalities
SRDF devices can dynamically swap “personality” between R1 and R2. After a
personality swap:
l
The R1 in the device pair becomes the R2 device, and
l
The R2 becomes the R1 device.
Swapping R1/R2 personalities allows the application to be restarted at the remote site
without interrupting replication if an application fails at the production site. After a
swap, the R2 side (now R1) can control operations while being remotely mirrored at
the primary (now R2) site.
An R1/R2 personality swap is not supported:
l
If the R2 device is larger than the R1 device.
l
If the device to be swapped is participating in an active SRDF/A session.
l
In SRDF/EDP topologies diskless R11 or R22 devices are not valid end states.
l
If the device to be swapped is the target device of any TimeFinder or EMC
Compatible flash operations.
SRDF modes of operation
SRDF modes of operation address different service level requirements and determine:
l
How R1 devices are remotely mirrored across the SRDF links.
l
How I/Os are processed.
l
When the host receives acknowledgment of a write operation relative to when the
write is replicated.
l
When writes “owed” between partner devices are sent across the SRDF links.
The mode of operation may change in response to control operations or failures:
l
The primary mode (synchronous or asynchronous) is the configured mode of
operation for a given SRDF device, range of SRDF devices, or an SRDF group.
l
The secondary mode is adaptive copy. Adaptive copy mode moves large amounts
of data quickly with minimal host impact. Adaptive copy mode does not provide
restartable data images at the secondary site until no new writes are sent to the R1
device and all data has finished copying to the R2.
Use adaptive copy mode to synchronize new SRDF device pairs or to migrate data to
another array. When the synchronization or migration is complete, you can revert to
the configured primary mode of operation.
Remote replication solutions
122 Product Guide VMAX 100K, VMAX 200K, VMAX 400K with HYPERMAX OS