ZFS optimization + Cache settings for VMs

[harmonyp]

I recently set up ZFS RAID-10 and I have some questions.

Generally speaking I presume this is a good setting for a mixture of Linux/Windows not particually running any processes to optimize (like SQL DB)

Also I have added the following

/etc/modprobe.d/zfs.conf

#Max Ram Used by ZFS - 64GB
options zfs zfs_arc_max=68719476736
#Min Ram Used by ZFS - 20GB
options zfs zfs_arc_min=2147483648

How can I check if this is being used? the nodes total RAM usage doesn't seem to be using much more than what the running VMs require.

And finally I recall reading that changing the cache settings from default (no cache) is required for snapshots? and is there better performances with ZFS if so what should I set it to for Windows + Linux VMs

 

[Dunuin]

How can I check if this is being used? the nodes total RAM usage doesn't seem to be using much more than what the running VMs require.

Run "arc_summary". It will give you a details usage of the ARC.

And finally I recall reading that changing the cache settings from default (no cache) is required for snapshots? and is there better performances with ZFS if so what should I set it to for Windows + Linux VMs

Snapshots are working fine with "default (no cache)".

 

[harmonyp]

Run "arc_summary". It will give you a details usage of the ARC.

Snapshots are working fine with "default (no cache)".

Thanks for the info.

What about caching should it be something specific for Windows/Linux?

 

[Dunuin]

What about caching should it be something specific for Windows/Linux?

As far as I know "no cache" is most of the time the best if you are working with ZFS so only the ARC is used and not another second cache that uses the RAM too, so stuff isn't caches twice. And your guest OS is caching too, so would be useless to cache everything 3 times in RAM.