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Partitioning of VMAX
I have a stituation where upper management has made decisions for Storage Upgrades where the technicians were not asked for their opinion. What came out of this is that we are replacing a VMAX with a VMAX 40K that has double the capacity. It also has double the cache. Currently the VMAX in place is the source box in an R1/R2 SRDF/A configuration. The R2 box is also being replaced, but it is not going to be doubled in size. The explanation from management is that the extra capacity on the R1 box is going to be used for non-SRDF workload. My fear is that with double the cache on the R1 side, we could potentially be looking for trouble on the R2 side. If the R1 size starts to fill up with writes, it could overload the R2 side. Is this a potential use for Dynamic Cache Partitioning? Could I partition part of the cache to the half of the box that will used for SRDF/A workloads, and the other half of the cache for the non-SRDF workload?
Fenglin1
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2 Intern
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2.1K Posts
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January 15th, 2014 18:00
Yes, you can enable DCP, by combining the SRDF/A Delta Set Extension (DSE) feature which extends the cache space available for an SRDF/A session by off-loading some or all of its cycle data from cache to preconfigured disk storage or pools.
I believe you'd better also consider some setting to avoid SRDF/A hit write pending limits:
rdfa_cache_percent: define the max# of system writing pending slots available for SRDF/A in order to ensure that the other applications can utilize some of WP limit
rdfa_host_throttle_time: When the system WP limit is reached , throttling will delay a write from the host until a cache slot becomes free.
See Solutions Enabler Symmetrix SRDF Famlily CLI Product Guide on EMC online support for the details.
christopher_ime
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January 14th, 2014 22:00
Please consider moving this question as-is (no need to recreate) to the proper forum for maximum visibility. Questions written to the users' own "Discussions" space don't get the same amount of attention and can go unanswered for a long time.
You can do so by selecting "Move" under ACTIONS along the upper-right. Then search for and select: "Symmetrix Support Forum".
Symmetrix Support Forum
sullysam1
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January 15th, 2014 03:00
Thanks for your help! I will do that!
sree_hari_karan
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January 16th, 2014 00:00
Yes, as mentioned above, rdfa_cache_percent will be the parameter to look out for. If you can tweak this value to the required levels, there will be a soft limit on the amount of cache available for the SRDF operations.
Thanks,
Sreehari
sauravrohilla
859 Posts
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January 16th, 2014 02:00
my take is to monitor the cache utilization on R1 side for some time. if you start to see it reaching to higher level then go for DCP. If you have healthy link and moderate workload, probably you'd never need to partition cache
regards,
Saurabh