Optane for caching + HDD for virtualisation

[Michelino]

Has anyone tried this combination for running multiple VM's off it? I'm looking to run a lot of VM's, like 50+. SSD can handle them all running at once without any issues, but how about optane + HDD. It will be a cheaper option, but I don't believe it can handle that many VM's cause HDD alone can handle only a few of them running at the same time. Anyone tried something similar?

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[IntelUser2000]

If IOPS are the limitation for supporting lots of VMs, then Optane caches may help, but you might still be limited depending on how large the cache size is.

You could try the 32GB model and return it if it doesn't work. However, the caching works for higher end Optane, so certainly you could buy the 280GB 900P and use that as a cache.

 

[Michelino]

I will definitely try it in the end, it might actually give a nice boost. The problem with higher capacity optane ssds is that they cost as much as Samsung enterprise ssd of a much higher capacity, and in that case it's much more sane to go Samsung.

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[arandomguy]

Would a larger drive even help? I thought Intel RST Cache itself currently has a maximum size limit (64gb?).

 

[IntelUser2000]

Would a larger drive even help? I thought Intel RST Cache itself currently has a maximum size limit (64gb?).

The RST caching has a 64GB limit. There's also an Optane specific caching that is different from it. It's better optimized for the Optane SSDs, and also takes the whole drive.

You can RST cache an Optane drive, so it can be used with 6th generation Core or older systems. It's only when you want to use the Optane specific caching you need 7th generation or later.

 

[gea]

A fast cache device for read/writes in front of a slow storage can improve performance but only if read/write load is not steady. In such a case the cache runs full and the whole system may become slower than without cache.

With VMs, your main concern should not only be performance but also data security as a crash during writes can corrupt data and filesystems.

I use Optane 800P and up (the smaller ones are too slow) in combination with HD Pools but only as log devices to protect the rambased writecache in my ZFS storage boxes. I also use them as an extension of the rambased readcache in ZFS.

While a multiple Raid-10 storage server say with 12 disks can give more than 1000 MB/s sequential async writes, this lowers to say 50-100 MB/s when you enable a secure sync write behavior to protect writes against a powerloss.

With an Optane (800P, 900P, 4800x) as an Slog (20GB partition is enough) sync write performance can go up to 500-800 MB/s. The rest of the Optane can be used as L2Arc readcache, as an ESXi bootdevice or for VMs as Optane performance is ok with a concurrent load.

see my benchemarks with ESXi at
https://napp-it.org/doc/downloads/optane_slog_pool_performane.pdf