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R1 HYPERMAX OS - R2 Enginuity 5876
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R1 Enginuity 5876 - R2 HYPERMAX OS
Enginuity 5773 to 5876
SRDF/A device-level pacing applies a write pacing delay for individual SRDF/A R1
devices whose R2 counterparts participate in TimeFinder copy sessions.
SRDF/A group-level pacing avoids high SRDF/A cache utilization levels when the R2
devices servicing both the SRDF/A and TimeFinder copy requests experience
slowdowns.
Device-level pacing avoids high SRDF/A cache utilization when the R2 devices
servicing both the SRDF/A and TimeFinder copy requests experience slowdowns.
Device-level pacing behavior varies depending on whether the maximum pacing delay
is specified or not specified:
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If the maximum write pacing delay is not specified, SRDF adds up to 50
milliseconds to the overall host write response time to keep the SRDF/A session
active.
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If the maximum write pacing delay is specified, SRDF adds up to the user-defined
maximum write pacing delay to keep the SRDF/A session active.
Device-level pacing can be activated on the second hop (R21 -> R2) of a cascaded
SRDF and cascaded SRDF/Star, topologies.
Device-level pacing may not take effect if all SRDF/A links are lost.
Write pacing and Transmit Idle
Host writes continue to be paced when:
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All SRDF links are lost, and
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Cache conditions require write pacing, and
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Transmit Idle is in effect.
Pacing during the outage is the same as the transfer rate prior to the outage.
SRDF read operations
Read operations from the R1 device do not usually involve SRDF emulations:
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For read “hits” (the production host issues a read to the R1 device, and the data is
in local cache), the host emulation reads data from cache and sends it to the host.
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For read “misses” (the requested data is not in cache), the drive emulation reads
the requested data from local drives to cache.
Refer to
Read operations from R2 devices
on page 136 for more information.
Read operations if R1 local copy fails
In SRDF/S, SRDF/A, and adaptive copy configurations, SRDF devices can process
read I/Os that cannot be processed by regular logical devices. If the R1 local copy
fails, the R1 device can still service the request as long as its SRDF state is Ready and
the R2 device has good data.
SRDF emulations help service the host read requests when the R1 local copy is not
available as follows:
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The SRDF emulations bring data from the R2 device to the host site.
Remote replication solutions
SRDF read operations
135
Summary of Contents for VMAX 100K
Page 1: ...EMC VMAX3 Family Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS REVISION 6 5 ...
Page 20: ...Preface 20 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
Page 46: ...VMAX3 with HYPERMAX OS 46 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
Page 72: ...Open systems features 72 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
Page 82: ...Provisioning 82 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
Page 158: ...Remote replication solutions 158 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
Page 186: ...Mainframe Error Reporting 186 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
Page 200: ...Licensing 200 Product Guide VMAX 100K VMAX 200K VMAX 400K with HYPERMAX OS ...
