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October 23rd, 2014 11:00
VNXe3200 Reccomendations
I currently use a VNXe3100 to serve up NFS shares to three VMWare ESXi hosts. It has 12 300 GB 15K drives all in a RAID5 performance pool. I have about 10 VM's on them serving mostly MS apps through RDP. I'm looking at budgeting a new VNXe for next year and was thinking about the VNXe3200. I have a question about FAST Cache and FAST VP.
In a traditional file server environment, I can see where FAST Cache and FAST VP would help put the hot data on the SSD's while keeping the less used data on HD's, but in a pure NFS - ESXi environment, how does this work since the datastore is treated as one big file? Does it move the entire VM to SSD's? If so, unless your VM is under 200 GB, I'm not sure how it would help.
Anyone care to enlighten me on how FAST Cache would help in this environment? I am especially interested in how this would help my SQL server.
Best Regards.
brettesinclair
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October 23rd, 2014 17:00
Hi, Fastcache does not work at an actual 'file' level so your vm/vmdks/datastore do not get treated as a whole cacheable object as such. System analyzes 64KB chunks of data and if accessed 3 times during in a measured period it is copied into fast cache so it can be accessed significantly quicker.
So think of it as moving chunks/blocks of hot data as opposed to files & folders. It does not take away the need to properly
design your sql environments.
Fast cache and fast vp work together and are complimentary technologies. If you have both, then data that has been promoted into SSD at a pool level by Fast VP will not be moved into Fast cache. Fast Cache is also considerably more granular as VP moves data in 256MB chunks instead of 64KB page.
It's generally a recommendation that if you have limited amounts of SSD, FastCache gives the bigger bang for buck.
What benefits will you see for SQL? It depends on many factors and even the SQL version. the way memory is used/allocated for working sets has evolved and improved significantly, which impacts how much actual hot data will be served out of host memory or from the array. Generally though you could expect an improvement in tps.
Recommended reading:
https://support.emc.com/docu53321_White-Paper:-Introduction-to-the-VNXe3200-FAST-Suite.pdf?language=en_US
Edit:Thanks Charles
reedic
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October 24th, 2014 00:00
One correction... FAST VP operates at the 256MB slice level, and FAST Cache operates at the 64KB page level.
pkilian-chipmancorp.com
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October 24th, 2014 08:00
Brett,
Thanks for clearing that up for me. It now makes more sense.
Best Regards.