Session priority the priority used to determine which

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Session priority = The priority used to determine which SRDF/A sessions to drop if cache becomes full. Values range from 1 to 64, with 1 being the highest priority (last to be dropped). Minimum Cycle Time = The minimum time to wait before attempting an SRDF/A cycle switch. Values range from 1 to 59 seconds, minimum is 3 for MSC. The default minimum cycle time is 15 seconds. There are group level parameters for SRDF/A DSE and SRDF/A Write Pacing. We will discuss them later in the module. SRDF/Asynchronous Operations
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22 Copyright 2015 EMC Corporation. All rights reserved. Each VMAX family array has an array-wide Max # of System Write Pending Slots limit (generally calculated as 75% of available cache slots). The purpose of this limit is to ensure that cache is not filled with Write Pending (WP) tracks, potentially preventing fast writes from hosts, because there is no place to put the I/O in cache. SRDF/A creates WP tracks as part of each cycle. SRDF/Asynchronous Operations
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23 Copyright 2015 EMC Corporation. All rights reserved. Examples are displayed in the following slides. SRDF/Asynchronous Operations
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24 Copyright 2015 EMC Corporation. All rights reserved. This output was captured from the R1 side. The Active Cycle is the Capture and the Inactive is the Transmit, as this output is from the R1 (source) perspective. From the R2 perspective the Active Cycle is Apply and the Inactive is Receive. The Cycle Size attribute Shared is applicable to Concurrent SRDF with both legs in SRDF/A mode. It represents the amount of shared cache slots between the two legs. Legend for Session Flags: T(ype) : 1 = RDF1, 2 = RDF2 A(SYNC) : Y = Yes, N = No S(tatus) : A = Active, I = Inactive, - = N/A Legend for the Attribute of Cycle Size: RDF1: Active = Capture Inactive = Transmit RDF2: Active = Apply Inactive = Receive SRDF/Asynchronous Operations
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25 Copyright 2015 EMC Corporation. All rights reserved. The Cache Slots available for all SRDF/A sessions is 75% of the System Write Pending Limit (541829/722439). SRDF/Asynchronous Operations
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26 Copyright 2015 EMC Corporation. All rights reserved. This lesson covered SRDF/A multi-cycle mode on VMAX3 arrays. The attributes that can be set for SRDF/A at a system and group level were discussed in detail. Method for adding/removing RDF device pairs to/from active SRDF/A sessions and monitoring SRDF/A were also presented. SRDF/Asynchronous Operations
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27 Copyright 2015 EMC Corporation. All rights reserved. This lesson covers SRDF/A resiliency features such as Transmit Idle, Delta Set Extension, and Group-level Write Pacing. Method for recovering after a link loss is also discussed. SRDF/Asynchronous Operations
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28 Copyright 2015 EMC Corporation. All rights reserved. SRDF/A Transmit Idle is a feature of SRDF/A that provides it with the capability of dynamically and transparently extending the Capture, Transmit, and Receive phases of the SRDF/A cycle while masking the effects of an “all SRDF links lost” event. Without the SRDF/A Transmit Idle feature, an “all SRDF links lost” event would normally result in the abnormal termination of SRDF/A. SRDF/A would become inactive. The SRDF/A
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