ZFS on a single disk?

[Šimun Mikecin]

2011/3/2 Ollivier Robert <roberto at keltia.freenix.fr>

> According to Dr Josef Karthauser:
> > I guess I should have been a bit clearer, I mean without any external
> devices backing them. Seeing as this is to be running on a VPS/Xen at a
> hosting environment I'm not able to add any additional devices.
>
> It will work even w/o anything added.  I've run an amd64 VM for several
> months like that.
>
> > I'm not memory starved however. Is it madness to use a memory disk? (The
> instance in question will have 6gb of ram total to play with.).
>
> You could use an md device to serve as a cache but with only 6 GB, just let
> ZFS use whatever it needs.
>

ZFS cache device (L2ARC) are beneficial when their size can be much larger
than size of your ARC cache. If you have much RAM, use it for ARC. L2ARC
acts like an extension of ARC, but is slower than ARC.
It would really be madness to use that RAM for a memory disk on which you
configure a ZFS cache device (L2ARC).