ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks

[Jean-Yves Avenard]

Hi

On 7 January 2011 00:45, Daniel Kalchev <daniel at digsys.bg> wrote:
> For pure storage, that is a place you send/store files, you don't really
> need the ZIL. You also need the L2ARC only if you read over and over again
> the same dataset, which is larger than the available ARC (ZFS cache memory).
> Both will not be significant for 'backup server' application, because it's
> very unlikely to do lots of SYNC I/O (where separate ZIL helps), or serve
> the same files back (where the L2ARC might help).
>
> You should also know that having large L2ARC requires that you also have
> larger ARC, because there are data pointers in the ARC that point to the
> L2ARC data. Someone will do good to the community to publish some reasonable
> estimates of the memory needs, so that people do not end up with large but
> unusable L2ARC setups.
>
> It seems that the upcoming v28 ZFS will help greatly with the ZIL in the
> main pool..

yes, it made a *huge* difference for me.. It went from "way too slow
to comprehend what's going on" to "still slow but I can live with it"

and I found no significant difference between ZIL on the main pool and
on a separate SSD