EMC VMAX 100K, Руководство по эксплуатации продукта

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Synchronous mode
SRDF/S maintains a real-time mirror image of data between the R1 and R2 devices
over distances of ~200 km or less.
Host writes are written simultaneously to both arrays in real time before the
application I/O completes. Acknowledgments are not sent to the host until the data is
stored in cache on both arrays.
Refer to Write operations in synchronous mode on page 127 and SRDF read
operations on page 135 for more information.
Asynchronous mode
SRDF/Asynchronous (SRDF/A) maintains a dependent-write consistent copy
between the R1 and R2 devices across any distance with no impact to the application.
Host writes are collected for a configurable interval into “delta sets”. Delta sets are
transferred to the remote array in timed cycles.
SRDF/A operations vary depending on whether the SRDF session mode is single or
multi-session with Multi Session Consistency (MSC) enabled:
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For single SRDF/A sessions, cycle switching is controlled by Enginuity. Each
session is controlled independently, whether it is in the same or multiple arrays.
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For multiple SRDF/A sessions in MSC mode, multiple SRDF groups are in the same
SRDF/A MSC session. Cycle switching is controlled by SRDF host software to
maintain consistency.
Refer to SRDF/A MSC cycle switching on page 130 for more information.
Adaptive copy modes
Adaptive copy modes:
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Transfer large amounts of data without impact on the host.
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Transfer data during data center migrations and consolidations, and in data
mobility environments.
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Allow the R1 and R2 devices to be out of synchronization by up to a user-
configured maximum skew value. If the maximum skew value is exceeded, SRDF
starts the synchronization process to transfer updates from the R1 to the R2
devices
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Are secondary modes of operation for SRDF/S. The R1 devices revert to SRDF/S
when the maximum skew value is reached and remain in SRDF/S until the number
of tracks out of synchronization is lower than the maximum skew.
There are two types of adaptive copy mode:
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Adaptive copy disk on page 123
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Adaptive copy write pending on page 124
Note
Adaptive copy write pending mode is not supported when the R1 side of an SRDF
device pair is on an array running HYPERMAX OS.
Adaptive copy disk
In adaptive copy disk mode, write requests accumulate on the R1 device (not in
cache). A background process sends the outstanding write requests to the
Remote replication solutions
SRDF modes of operation 123