Date: Thu, 18 Feb 2021 20:08:51 -0500 From: Jeremy Faulkner <gldisater@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: Reading a corrupted file on ZFS Message-ID: <92c03e85-4014-b5ee-17a5-bac3902678cb@gmail.com> In-Reply-To: <da892eeb-233f-551f-2faa-62f42c3c1d5b@artem.ru> References: <da892eeb-233f-551f-2faa-62f42c3c1d5b@artem.ru>
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ZDB can be used to pull individual blocks out of a zpool to allow you to piece together what's left of your file. https://www.youtube.com/watch?v=y7gQwypNMdk https://gist.github.com/mdimura/5aa4c163a7e0856b3712b6a880670678 On 2021-02-12 9:53 a.m., Artem Kuchin wrote: > I did a little experiment > > I have a mirror ZFS pool called ZDATA, i created a file and damanged the > same byte in file in it on both disks. > > File has ABCDEF string. > > > ZDATA ONLINE 0 0 0 > mirror-0 ONLINE 0 0 0 > ada0 ONLINE 0 0 1 > ada1 ONLINE 0 0 0 > > > destroy ZDATA > > on ada0 change A to Z > on ada1 change A to Y > reimport > > root@xigmanas:~# zpool status > pool: ZDATA > state: ONLINE > scan: scrub repaired 24K in 0 days 00:03:01 with 0 errors on Fri Feb > 12 16:48:46 2021 > config: > > NAME STATE READ WRITE CKSUM > ZDATA ONLINE 0 0 0 > mirror-0 ONLINE 0 0 0 > ada0 ONLINE 0 0 0 > ada1 ONLINE 0 0 0 > > errors: No known data errors > > Hmm. it repaired something. Read data from disks. > ada0 - Z > ada1 - Y > so, that repair was not the rotten bytes. > > Now run scrub > > root@xigmanas:~# zpool status -v ZDATA > pool: ZDATA > state: ONLINE > status: One or more devices has experienced an error resulting in data > corruption. Applications may be affected. > action: Restore the file in question if possible. Otherwise restore the > entire pool from backup. > see:http://illumos.org/msg/ZFS-8000-8A > <http://illumos.org/msg/ZFS-8000-8A>; > scan: scrub repaired 0 in 0 days 00:03:02 with 1 errors on Fri Feb 12 > 16:59:49 2021 > config: > > NAME STATE READ WRITE CKSUM > ZDATA ONLINE 0 0 1 > mirror-0 ONLINE 0 0 2 > ada0 ONLINE 0 0 2 > ada1 ONLINE 0 0 2 > > errors: Permanent errors have been detected in the following files: > > /data/DATASET1/test.file > > the data is still Z and Y, not sync-ed. > > I cannot read or write this file. This is bad. > > zfs set checksum=off ZDATA > > did not help, still cannot read or write the file. > > zpool clear -F ZDATA > > still cannot r/w the file > > Now i am stuck in worst situation that with UFS - i cannot read what's > left of this file. > > I deleted the file and the scrubbed - error went away. But i lost the file. > > So, the question is how to read the file with an error ? I googled for 2 > hours and still did not find a solution. > > > Artem > > _______________________________________________ > freebsd-fs@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" -- -- Jeremy Faulkner
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