It well may be that different methods are optimal for different use cases. Mechanical disk vs. SSD; mirrored vs. raidz[123]; sparse vs. populated; etc.
It would be interesting to read more in this area, if papers are available. I'll have to take a look. ... Or does someone have pointers? Mark On Dec 20, 2010, at 6:28 PM, Edward Ned Harvey wrote: >> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- >> boun...@opensolaris.org] On Behalf Of Erik Trimble >> >>> In the case of resilvering on a mirrored disk, why not take a snapshot, > and >> then >>> resilver by doing a pure block copy from the snapshot? It would be >> sequential, >> >> So, a >> ZFS snapshot would be just as fragmented as the ZFS filesystem was at >> the time. > > I think Mark was suggesting something like "dd" copy device 1 onto device 2, > in order to guarantee a first-pass sequential resilver. And my response > would be: Creative thinking and suggestions are always a good thing. In > fact, the above suggestion is already faster than the present-day solution > for what I'm calling "typical" usage, but there are an awful lot of use > cases where the "dd" solution would be worse... Such as a pool which is > largely sequential already, or largely empty, or made of high IOPS devices > such as SSD. However, there is a desire to avoid resilvering unused blocks, > so I hope a better solution is possible... > > The fundamental requirement for a better optimized solution would be a way > to resilver according to disk ordering... And it's just a question for > somebody that actually knows the answer ... How terrible is the idea of > figuring out the on-disk order? > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
