Do you have to use a cache tier with vSAN?

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Evan

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Jan 6, 2016
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Bit silly right but yes that’s the way it is.
Remember was developed before NVMe disks were available.
 

SRussell

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Oct 7, 2019
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Bit silly right but yes that’s the way it is.
Remember was developed before NVMe disks were available.
Appreciate any feedback. I am trying to keep my lab costs as low as possible. I am looking for anywhere I can lessen the number of parts without impacting performance too much.
 

Evan

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Jan 6, 2016
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Can reduce the size of the disk. Smaller size usually = less performance though.
It’s a pretty good minimal config for a modern cluster.
Using older SAS SSD in a bigger chassis for vSAN can make cheaper options I am sure but the appeal of that config is size, power consumption, performance and reasonable cost.
 

Evan

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Jan 6, 2016
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Maybe you can partition NVMe to put the cache and data on the same device ? I read somebody else has done that.
 

Rand__

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Mar 6, 2014
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Maybe you can partition NVMe to put the cache and data on the same device ? I read somebody else has done that.
I don't think that will work as vSan wants to use the whole disk - it won't accept pre-partitioned disks.

Also bear in mind that with an All Flash setup your cache drive will decide your write performance while the capacity drive will decide your read performance.
 

Evan

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Jan 6, 2016
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I don't think that will work as vSan wants to use the whole disk - it won't accept pre-partitioned disks.

Also bear in mind that with an All Flash setup your cache drive will decide your write performance while the capacity drive will decide your read performance.
sorry I should have said namespace rather than partition. NVMe namespaces ‘should’ appear as separate disks to vSAN
Intel SSD as I know don’t support multi-namespace but some others like HGST do...
 

Rand__

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Mar 6, 2014
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That might work if you can set these up at device or bios level - but thats going to need hardware thats capable of it which might defeat the idea of cheap (no idea which would, couldnt find much on a quick search)
 

Spartacus

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May 27, 2019
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Maybe you can partition NVMe to put the cache and data on the same device ? I read somebody else has done that.
vSAN is a software raid solution, it works the similar to FreeNAS, unRAID or the like with JBOD.
I don't believe you can split a drive for SSD and Data, if you could make it work, it would wreck any standardization hope of support/troubleshooting, not recommended.

You can however use a configuration edit to 'mark' drives as SSD to trick it into thinking it has them.
 
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CaptainPoundSand

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Mar 16, 2019
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sorry I should have said namespace rather than partition. NVMe namespaces ‘should’ appear as separate disks to vSAN
Intel SSD as I know don’t support multi-namespace but some others like HGST do...
NVME disks are hit/miss for namespace support. (M.2 do not, some newer intel do)

I'm currently have 3x ESXI hosts with 1x NVME 1725b spit into 5 name spaces each, so I have 1x 600gb Cache, and 4x 590GB capacity drives. VSAN see's it fairly easily.


VMware vSAN + NVMe namespace magic: Split 1 SSD into 24 devices for great storage performance