Re: [zfs-discuss] PSARC recover files?
Say I end up with a handful of unrecoverable bad blocks that just so happen to be referenced by ALL of my snapshots (in some file that's been around forever). Say I don't care about the file or two in which the bad blocks exist. Is there any way to purge those blocks from the pool (and all snapshots) without having to restore the whole pool from backup? -- This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
On Tue, Nov 10, 2009 at 2:40 PM, BJ Quinn bjqu...@seidal.com wrote: Say I end up with a handful of unrecoverable bad blocks that just so happen to be referenced by ALL of my snapshots (in some file that's been around forever). Say I don't care about the file or two in which the bad blocks exist. Is there any way to purge those blocks from the pool (and all snapshots) without having to restore the whole pool from backup? No. The whole point of a snapshot is to keep a consistent on-disk state from a certain point in time. I'm not entirely sure how you managed to corrupt blocks that are part of an existing snapshot though, as they'd be read-only. The only way that should even be able to happen is if you took a snapshot after the blocks were already corrupted. Any new writes would be allocated from new blocks. --Tim ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
On Tue, Nov 10, 2009 at 03:04:24PM -0600, Tim Cook wrote: No. The whole point of a snapshot is to keep a consistent on-disk state from a certain point in time. I'm not entirely sure how you managed to corrupt blocks that are part of an existing snapshot though, as they'd be read-only. Physical corruption of the media Something outside of ZFS diddling bits on storage The only way that should even be able to happen is if you took a snapshot after the blocks were already corrupted. Any new writes would be allocated from new blocks. It can be corrupted while it sits on disk. Since it's read-only, you can't force it to allocate anything and clean itself up. -- Darren ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
On Tue, Nov 10, 2009 at 3:19 PM, A Darren Dunham ddun...@taos.com wrote: On Tue, Nov 10, 2009 at 03:04:24PM -0600, Tim Cook wrote: No. The whole point of a snapshot is to keep a consistent on-disk state from a certain point in time. I'm not entirely sure how you managed to corrupt blocks that are part of an existing snapshot though, as they'd be read-only. Physical corruption of the media Something outside of ZFS diddling bits on storage The only way that should even be able to happen is if you took a snapshot after the blocks were already corrupted. Any new writes would be allocated from new blocks. It can be corrupted while it sits on disk. Since it's read-only, you can't force it to allocate anything and clean itself up. You're telling me a scrub won't actively clean up corruption in snapshots? That sounds absolutely absurd to me. --Tim ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
On Tue, Nov 10, 2009 at 03:33:22PM -0600, Tim Cook wrote: You're telling me a scrub won't actively clean up corruption in snapshots? That sounds absolutely absurd to me. Depends on how much redundancy you have in your pool. If you have no mirrors, no RAID-Z, and no ditto blocks for data, well, you have no redundancy, and ZFS won't be able to recover affected files. Nico -- ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
I believe it was physical corruption of the media. Strange thing is last time it happened to me it also managed to replicate the bad blocks over to my backup server replicated with SNDR... And yes, it IS read only, and a scrub will NOT actively clean up corruption in snapshots. It will DETECT corruption, but if it's unrecoverable, that's that. It's unrecoverable. If there's not enough redundancy in the pool, I'm ok with the data not being recoverable. But wouldn't there be a way to purge out the bad blocks if for example it was only in a single bad file out of millions of files, and I didn't care about the file in question? I don't want to recover the file, I want to have a working version of my pool+snapshots minus the tiny bit that was obviously corrupt. Barring another solution, I'd have to take the pool in question, delete the bad file, and delete ALL the snapshots. Then restore the old snapshots from backup to another pool, and copy over the current data from the pool that had a problem over to the new pool. I can get most of my snapshots back that way, with the best known current data sitting on top as the active data set. Problem is with hundreds of snapshots plus compression, zfs send/recv takes over 24 hours to restore a full backup like that to a new storage device. Last time this happened to me, I just had to say goodbye to all my snapshots and deal with it, all over a couple of kilobytes of temp files. -- This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
[zfs-discuss] PSARC recover files?
This new PSARC putback that allows to rollback to an earlier valid uber block is good. This immediately raises a question: could we use this PSARC functionality to recover deleted files? Or some variation? I dont need that functionality now, but I am just curious... -- This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
frequent snapshots offer outstanding oops protection. Rob ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
Maybe to create snapshots after the fact as a part of some larger disaster recovery effort. (What did my pool/file-system look like at 10am?... Say 30-minutes before the database barffed on itself...) With some enhancements might this functionality be extendable into a poor man's CDP offering that won't protect against (non-redundant) hardware failures, but can provide some relieve in App/Human creativity. Seems like one of those things you never really need... Until you have to that one time, at which point nothing else will do. One would think that using zdb and friends it might be possible to walk the chain of tx-logs backwards and each good/whole one could be a valid recover/reset-point. -- This raises a more fundamental question that perhaps someone can comment on. Does ZFS's COW follow a fairly strict last released-block, last overwritten model (keeping a maximum buffer of in tact data), or do previously used blocks get overwritten largely based on block/physical location, fragmentation/best-fit, etc?). In cases of blank disks/LUNs, does for instance a 1TB drive get completely COW-ed onto its blank-space, or does zfs re-use previously used (and freed) space before burning through then entire disk-space? Thanks, -- MikeE -Original Message- From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-boun...@opensolaris.org] On Behalf Of Orvar Korvar Sent: Monday, November 09, 2009 8:36 AM To: zfs-discuss@opensolaris.org Subject: [zfs-discuss] PSARC recover files? This new PSARC putback that allows to rollback to an earlier valid uber block is good. This immediately raises a question: could we use this PSARC functionality to recover deleted files? Or some variation? I dont need that functionality now, but I am just curious... -- This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
Maybe to create snapshots after the fact how does one quiesce a drive after the fact? ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] PSARC recover files?
+-- | On 2009-11-09 12:18:04, Ellis, Mike wrote: | | Maybe to create snapshots after the fact as a part of some larger disaster recovery effort. | (What did my pool/file-system look like at 10am?... Say 30-minutes before the database barffed on itself...) | | With some enhancements might this functionality be extendable into a poor man's CDP offering that won't protect against (non-redundant) hardware failures, but can provide some relieve in App/Human creativity. Alternatively, you can write a cronjob/service that takes snapshots of your important filesystems. I take hourly snaps of our all our homedirs, and five-minute snaps of our database volumes (InnoDB and Postgres both recover adequately; I have used these snaps to build recovery zones to pull accidentally deleted data from before; good times). Look at OpenSolaris' Time Slider service, although writing something that does this is pretty trivial (we use a Perl program with YAML configs launched by cron every minute). My one suggestion would be to ensure the automatically taken snaps have a unique name (@auto, or whatever), so you can do bulk expiry tomorrow or next week without worry. Cheers. -- bda cyberpunk is dead. long live cyberpunk. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
