Enhanced group level pacing responds only to

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Enhanced group-level pacing responds only to spillover rate on the R1 side, it is not affected by the spillover on the R2 side. All existing pacing features are supported and can be utilized to keep SRDF/A sessions active. Enhanced group-level pacing is supported between VMAX3 arrays and VMAX arrays running Enginuity 5876 with fix 67492. SRDF/Asynchronous Operations
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36 Copyright 2015 EMC Corporation. All rights reserved. The command examples show activating Group-level Write Pacing and setting Autostart “on”. The symrdf set rdfa_pace syntax can also be used to change the Write Pacing Delay and Threshold parameters. SRDF/Asynchronous Operations
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37 Copyright 2015 EMC Corporation. All rights reserved. Details of the SRDF Group shows the current status of Group-level write pacing. Write Pacing Flags : (GRP) Group-Level Pacing: ( S) tatus : A = Active , I = Inactive, - = N/A ( A )utostart : X = Enabled , . = Disabled, - = N/A S( U )pported : X = Supported , . = Not Supported, - = N/A (DEV) Device-Level Pacing: (S)tatus : A = Active, I = Inactive, - = N/A (A)utostart : X = Enabled, . = Disabled, - = N/A S(U)pported : X = Supported, . = Not Supported, - = N/A (FLG) Flags for Group-Level and Device-Level Pacing: Devs (P)aceable : X = All Devices, . = Not all devices, - = N/A SRDF/Asynchronous Operations
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38 Copyright 2015 EMC Corporation. All rights reserved. As noted earlier, during resynchronization, R2 does not have consistent data. A copy of the consistent R2 data prior to resynchronization can safeguard against unexpected failures during the resynchronization process. When the link is resumed, if there are a large number of invalid tracks owed by the R1 to its R2, it is recommended that SRDF/A not be enabled right away. Enabling SRDF/A right after link resumption causes a surge of traffic on the link due to (a) shipping of accumulated invalid tracks, and (b) the new data added to the SRDF/A cycles. This would lead to SRDF/A consuming more cache and reaching the System Write Pending limit. If this happens, SRDF/A would drop again. Like with SRDF/S, resynchronization should be performed during periods of relatively low production activity. Resynchronization in Adaptive Copy Disk mode minimizes the impact on the production host. New writes are buffered and these, along with the R2 invalids, are sent across the link. The time it takes to resynchronize is elongated. Resynchronization in Synchronous mode impacts the production host. New writes have to be sent preferentially across the link while the R2 invalids are also shipped. Switching to Synchronous is possible only if the distances and other factors permit. For instance, if the norm is to run in SRDF/S and toggle into SRDF/A for batch processing (due to higher bandwidth requirement). In this case, if a loss of links occurs during the batch processing, it might be possible to resynchronize in SRDF/S.
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