Unable to increase write cache on VNX7500 after code upgrade

Question

Per the Open Systems Configuration Guide, I am supposed to get up to 10,600MB of write cache with R32 and data services turned on.  However, I can only get 7,047MB.  Does any one know how I can get to 10,600MB?  Our SP cache is saturated right now, and we really could use the additional cache.  We have FAST Cache turned on, but I am thinking that the memory map of the FAST Cache is contributing to the issues I am having with the SP Cache as well.

brettesinclair · Answer

If I recall correctly, approximately 1.6MB of available DRAM is consumed for each GB of active FAST Cache.

Then there's the memory consumption from all the data services /enablers in use, which may be leaving you short of what you expect.

Are you seeing a high amount of forced-flushing ? Are the cache watermarks at the default ?

souvac · Answer

Thanks, Bret! This explains a lot. The customer has the maximum FAST Cache configured which is 2000GB. Based on the 1.6MB number you have, this explains the 3GB of DRAM I am missing. We’ll play with changing the size FAST Cache.

Charlie Souvannavong

Advisory Systems Engineer

EMC Corporation

Google: 703-996-9526

iPhone: 703-675-3093 ***Please Note New Number as of 10/1/2014***

VNX

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