If I create a mirror, presumably if possible I use two or more identically sized devices, since it can only be as large as the smallest. However, if later I want to replace a disk with a larger one, and detach the mirror (and anything else on the disk), replace the disk (and if applicable repartition it), since it _is_ a larger disk (and/or the partitions will likely be larger since they mustn''t be smaller, and blocks per cylinder will likely differ, and partitions are on cylinder boundaries), once I reattach everything, I''ll now have two different sized devices in the mirror. So far, the mirror is still the original size. But what if I later replace the other disks with ones identical to the first one I replaced? With all the devices within the mirror now the larger size, will the mirror and the zpool of which it is a part expand? And if that won''t happen automatically, can it (without inordinate trickery, and online, i.e. without backup and restore) be forced to do so? This message posted from opensolaris.org
Yes, this is supported now. Replacing one half of a mirror with a larger device; letting it resilver; then replacing the other half does indeed get a larger mirror. I believe this is described somewhere but I can''t remember where now. Neil. Richard L. Hamilton wrote On 03/23/07 20:45,:> If I create a mirror, presumably if possible I use two or more identically sized devices, > since it can only be as large as the smallest. However, if later I want to replace a disk > with a larger one, and detach the mirror (and anything else on the disk), replace the > disk (and if applicable repartition it), since it _is_ a larger disk (and/or the partitions > will likely be larger since they mustn''t be smaller, and blocks per cylinder will likely differ, > and partitions are on cylinder boundaries), once I reattach everything, I''ll now have > two different sized devices in the mirror. So far, the mirror is still the original size. > But what if I later replace the other disks with ones identical to the first one I replaced? > With all the devices within the mirror now the larger size, will the mirror and the zpool > of which it is a part expand? And if that won''t happen automatically, can it (without > inordinate trickery, and online, i.e. without backup and restore) be forced to do so? > > > This message posted from opensolaris.org > _______________________________________________ > zfs-discuss mailing list > zfs-discuss at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
> Yes, this is supported now. Replacing one half of a > mirror with a larger device; > letting it resilver; then replacing the other half > does indeed get a larger mirror. > I believe this is described somewhere but I can''t > remember where now.Thanks; I sure didn''t see the answer on the zpool man page, and if it''s in the admin guide, I must have missed it. In fact, I''m not seeing it in the code either, but this is the first time I''ve looked at the zfs code, and I haven''t exactly read all of it, let alone understood it as a whole. It strikes me as useful to be able to expand the storage that way (since one tends to have to replace disks anyway, and if the same model isn''t available, the new ones will likely be larger), although as disks grow larger, I suppose one might also want to consider adding more redundancy. Since I only have 2 to work with, that''s not really an option. :-) Anyway, I hope that will eventually be mentioned (or more prominently, if it''s already there) in the admin guide, and perhaps even on the zpool man page. I suppose there''s no way to tell zfs to shrink its use of a device down to a certain size, releasing space at the end if possible. While that''s probably much less important, if one gets into a real jam, it might still be desirable. This message posted from opensolaris.org