separate boot zfs and storage zfs

[geronimobb]

Hy all,

is there any performance win or other advantage with a separate zfs pool for boot and zfs pool for storage (vm, container).
Till now i always builded upon 1 zfs pool for boot and storage.

Kind regards and thanks for any advice

 

[alexskysilk]

performance may or may not be meaningfully affected but its best practice to keep your boot device(s) and data device(s) separate in case the boot device fails/dies or you want to move the data to another os/hardware.

 

[guletz]

is there any performance win

... in most cases, the performances will be bad, because using 2 different zfs pools, will reduce the ARC cache usable for each pool(assumming that you will alocate the default, around 50% total RAM). The only case that I can imagine to be acceptable(for performance point of view + saftey) will be to have one zfs pool using 2xSSD(mirror), with ARC for metadata only and another zfs pool(with whatever ....).

 

[geronimobb]

Thanks, i suspected allready that more zfs pools would have consequences on the ARC cache.
Would a separate ssd for cache (l2) and log be beneficial then?
A single ssd with ext4 for booting proxmox only seems the alternative, but you sacrifice redundancy on the booting device then.
Not a perfect world...

 

[guletz]

Would a separate ssd for cache (l2) and log be beneficial then?

Maybe, but could be many variables in this case(load, pattern acces, RAM, and so on)! As a general rule any spcialize cache system(like OS cache in VM) is better compared with a general volum maneger cache sistem. Also the VM OS cache it very close to the source of data, and have a better chance to know what and when to cache the data.

So for this point of view, I think is better to use ARC only for metadata, so you will use not so much RAM(ARC), and then you can allocate supplimentary RAM for your VMs(better cache = better RAM usage). But also this ideea, is not 100% fail-safe!