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MJMVCIX
Enthusiast
Enthusiast

vSAN All Flash Cache Sizing

Hi All, 

This link: https://core.vmware.com/resource/vmware-vsan-design-guide#sec6843-sub5 details the cache sizes and details this: 

"Here are a table showing endurance classes and the total write buffer needed per host."

Is the above correct that this is per host? Should it not be per disk group?

Thanks

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TheBobkin
Champion
Champion

@MJMVCIX, Those are referencing different ReadyNode performance profile builds e.g. AF-8, AF-6 and AF-4, so yes these are per host.

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MJMVCIX
Enthusiast
Enthusiast

Ok so even considering the most demanding workload - 100% write sequential with an AF8, as an example, you could have 4 disk groups, each with just a 400Gb Cache Drive each?

If the above is right then with vSphere/vSAN 8 able to use up to 1.6TB of the Cache tier, it sounds like going a 1.6Tb cache would only be fully justified if you have 1 disk group for 100% write sequential with an AF8 as 1.6TB cache is the guideline per host?

For the above, having lets say 3 x disk groups with 1.6Tb cache disks wouldn't be justified?

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