[pve-devel] Fwd: Re: recommanded cache setting for rbd image

[Stefan Priebe - Profihost AG]

Hello list,

inktank recommands using writeback mode for rbd by default. As it is 
safe like a normal harddisk with it's cache.

What do you think?

Greets
Stefan


> Hello list,
>
> right now i'm testing rbd block devices with kvm using Default cache (no
> cache).
>
> Is there any recommanded value for RBD? (i don't wanna loose data)

It acts like a well-behaved disk cache (i.e. it respects
flushes/barriers from the guest), so it's no more likely to cause data
loss than a local hard disk in the event of an unexpected shutdown.

I recommend running it in writeback mode (the default when rbd cache =
true). The best cache size will depend on your workload and hardware.