On Feb 6, 2013, at 5:17 PM, Gregg Wonderly <gregg...@gmail.com> wrote:
> This is one of the greatest annoyances of ZFS. I don't really understand > how, a zvol's space can not be accurately enumerated from top to bottom of > the tree in 'df' output etc. Why does a "zvol" divorce the space used from > the root of the volume? Thick (with reservation) or thin provisioning behave differently. Also, depending on how you created the reservation, it might or might not account for the metadata overhead needed. By default, space for metadata is reserved, but if you use the -s (sparse aka thin provisioning) option, then later reservation changes are set as absolute. Also, metadata space, compression, copies, and deduplication must be accounted for. The old notions of free/available don't match very well with these modern features. > > Gregg Wonderly > > On Feb 6, 2013, at 5:26 PM, Edward Ned Harvey > (opensolarisisdeadlongliveopensolaris) > <opensolarisisdeadlongliveopensola...@nedharvey.com> wrote: > >> I have a bunch of VM's, and some samba shares, etc, on a pool. I created >> the VM's using zvol's, specifically so they would have an >> appropriaterefreservation and never run out of disk space, even with >> snapshots. Today, I ran out of disk space, and all the VM's died. So >> obviously it didn't work. >> >> When I used "zpool status" after the system crashed, I saw this: >> NAME SIZE ALLOC FREE EXPANDSZ CAP DEDUP HEALTH ALTROOT >> storage 928G 568G 360G - 61% 1.00x ONLINE - >> >> I did some cleanup, so I could turn things back on ... Freed up about 4G. >> >> Now, when I use "zpool status" I see this: >> NAME SIZE ALLOC FREE EXPANDSZ CAP DEDUP HEALTH ALTROOT >> storage 928G 564G 364G - 60% 1.00x ONLINE - >> >> When I use "zfs list storage" I see this: >> NAME USED AVAIL REFER MOUNTPOINT >> storage 909G 4.01G 32.5K /storage >> >> So I guess the lesson is (a) refreservation and zvol alone aren't enough to >> ensure your VM's will stay up. and (b) if you want to know how much room is >> *actually* available, as in "usable," as in, "how much can I write before I >> run out of space," you should use "zfs list" and not "zpoolstatus" Correct. zpool status does not show dataset space available. -- richard -- richard.ell...@richardelling.com +1-760-896-4422
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