On Jan 21, 2010, at 4:32 PM, Daniel Carosone wrote: >> I propose a best practice of adding the cache device to rpool and be >> happy. > > It is *still* not that simple. Forget my slow disks caching an even > slower pool (which is still fast enough for my needs, thanks to the > cache and zil). > > Consider a server config thus: > - two MLC SSDs (x25-M, OCZ Vertex, whatever) > - SSDs partitioned in two, mirrored rpool & 2x l2arc > - a bunch of disks for a data pool > > This is a likely/common configuration, commodity systems being limited > mostly by number of sata ports. I'd even go so far as to propose it > as another best practice, for those circumstances.
> Now, why would I waste l2arc space, bandwidth, and wear cycles to > cache rpool to the same ssd's that would be read on a miss anyway? > > So, there's at least one more step required for happiness: > # zfs set secondarycache=none rpool > > (plus relying on property inheritance through the rest of rpool) I agree with this, except for the fact that the most common installers (LiveCD, Nexenta, etc.) use the whole disk for rpool[1]. So the likely and common configuration today is moving towards one whole root disk. That could change in the future. [1] Solaris 10? well... since installation hard anyway, might as well do this. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
