Improve NVME Performance

grasgruen.it · Tue Nov 10, 2020 3:54 pm

Hi,

I am running Starwind vSAN Free on Hyper-V 2019 Server on a AMD X570 hardware (which is not really supported). It runs good besides the disk performance. Had to use Win10 drivers for chipset. No question marks in devmgmt besides audio devices. The disk is a Corsair Force MP600.

Diskspd 4k results without disk cache are bad (13MB/s).
diskspd.exe -c100G -t12 -si -b4K -d30 -L -o16 -w100 -D -h e:\testfile.dat

64k results are OK (184MB/s).
diskspd.exe -c100G -t12 -si -b64K -d30 -L -o16 -w100 -D -h e:\testfile.dat

4K test using disk cache is good (1046MB/s)
diskspd.exe -c100G -t12 -si -b4K -d30 -L -o16 -w100 -D e:\testfile.dat

Is it true, that the 4k test without using cache is the most relevant for vSAN on Hyper-V ?
Any chance to use the disk cache for vSAN?
Any ideas to improve the performance?

Thank you

Tue Nov 10, 2020 6:59 pm

Thanks for your question and welcome to StarWind Forum. Yes, try enabling disk cache.

May I wonder what is the network card you use?
Also, what is the underlying storage performance you got with diskspd?
Was there any production running on those hosts?

See the benchmarking recommendations here https://www.starwindsoftware.com/best-p ... practices/

grasgruen.it · Fri Nov 13, 2020 9:51 am

My test results are from the underlying storage. Tested locally on the server. No vSAN active yet.
How could I activate the hardware disk cache? I know only how to define RAM and SSD cache in vSAN.

Thank you

Fri Nov 13, 2020 11:21 am

Greetings,

Hardware caching should be activated on the disks.

grasgruen.it · Fri Nov 13, 2020 1:43 pm

H/W Caching is active.
Is in this case the diskspd test of the storage with caching (without the switch -h) relevant?

Is the Starwind vSAN able to use the hardware cache of an NVME SSD?
Why is then the recommended storagetest without cache?
https://www.starwindsoftware.com/best-p ... practices/

Fri Nov 13, 2020 2:22 pm

Is in this case the diskspd test of the storage with caching (without the switch -h) relevant?

Yes, if you test with a +50 GB file.

Is the Starwind vSAN able to use the hardware cache of an NVME SSD?

No, this is a whole different layer and StarWind VSAN does not use it. But, it might benefit from it.

Why is then the recommended storagetest without cache?

That is RAM cache, not disk cache. We recommend disabling it so RAM does not alter the performance of the underlying storage. Write-back RAM caching normally brings a modest performance boost for flash arrays so we often leave it disabled for SSDs. For testing purposes, you can enable RAM caching though (that's why we call it a test after all

). But, RAM amount should be 1 GB per 1 TB of HA device capacity or more. You can learn more about RAM caching in StarWind VSAN here https://knowledgebase.starwindsoftware. ... rinciples/. Make sure to have a big enough test file if you are using RAM cache.