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

Damien Fleuriot ml at my.gd
Thu Jan 6 19:45:34 UTC 2011

On 6 January 2011 14:45, 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..
> You need to experiment with the L2ARC (this is safe with current v14 and v15
> pools) to see if your usage will see benefit from it's use. Experimenting
> with ZIL currently requires that you recreate the pool. With the
> experimental v28 code things are much easier.

I see, thanks for the pointers.

The thing is, this will be a home storage (samba share, media server)
box, but I'd also like to experiment a bit, and it seems like a waste
to not try at least the cache, seeing I'll have a SSD at hand.

If things go well, I may be able to recommend ZFS for production
storage servers at work and I'd really like to know how the cache and
ZIL work at that time ;)

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