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<p class="MsoNormal">I’m only showing you the last 10 directories below but there are about 30 or 40 directories with a pretty uniform distribution between 6/20 and now. If it was a situation where we had been rolled back to 6/20 but directories were starting
to be updated again, there should be a big gap with no updates. The rollback (when we deleted the “snapshot”) happened on Monday, 9/18. We could do another snapshot of the MDT, mount it read only and poke around in there if you think that would help. Actually,
our backup process (which is running normally again) is doing just that. It takes quite a long time to complete so there is opportunity for me to investigate.
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">Andreas Dilger <adilger@whamcloud.com><br>
<b>Date: </b>Friday, September 22, 2023 at 1:36 AM<br>
<b>To: </b>"Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.]" <darby.vicker-1@nasa.gov><br>
<b>Cc: </b>"lustre-discuss@lists.lustre.org" <lustre-discuss@lists.lustre.org><br>
<b>Subject: </b>Re: [EXTERNAL] Re: [lustre-discuss] Data recovery with lost MDT data<o:p></o:p></span></p>
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<b><span style="font-size:10.0pt;color:black">CAUTION:</span></b><span style="color:black">
</span><span style="font-size:10.0pt;color:black">This email originated from outside of NASA. Please take care when clicking links or opening attachments. Use the "Report Message" button to report suspicious messages to the NASA SOC.</span><span style="color:black">
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<p class="MsoNormal">On Sep 21, 2023, at 16:06, Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] <<a href="mailto:darby.vicker-1@nasa.gov">darby.vicker-1@nasa.gov</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">I knew an lfsck would identify the orphaned objects. That’s great that it will move those objects to an area we can triage. With ownership still intact (and I assume time stamps too), I think this will be helpful for at least some of
the users to recover some of their data. Thanks Andreas. <span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">I do have another question. Even with the MDT loss, the top level user directories on the file system are still showing current modification times. I was a little surprised to see this – my expectation was that the most current time would
be from the snapshot that we accidentally reverted to, 6/20/2023 in this case. Does this make sense? <span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">The timestamps of the directories are only stored on the MDT (unlike regular files which keep of the timestamp on both the MDT and OST). Is it possible that users (or possibly recovered clients with existing mountpoints) have started to
access the filesystem in the past few days since it was recovered, or an admin was doing something that would have caused the directories to be modified?<o:p></o:p></p>
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<p class="MsoNormal">Is it possible you have a newer copy of the MDT than you thought?<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">[dvicker@dvicker ~]$ ls -lrt /ephemeral/ | tail</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwx------ 2 abjuarez abjuarez 4096 Sep 12 13:24 abjuarez/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwxr-x--- 2 ksmith29 ksmith29 4096 Sep 13 15:37 ksmith29/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwxr-xr-x 55 bjjohn10 bjjohn10 4096 Sep 13 16:36 bjjohn10/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwxrwx--- 3 cbrownsc ccp_fast 4096 Sep 14 12:27 cbrownsc/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwx------ 3 fgholiza fgholiza 4096 Sep 18 06:41 fgholiza/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwx------ 5 mtfoste2 mtfoste2 4096 Sep 19 11:35 mtfoste2/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwx------ 4 abenini abenini 4096 Sep 19 15:33 abenini/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> 4 drwx------ 9 pdetremp pdetremp 4096 Sep 19 16:49 pdetremp/</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">[dvicker@dvicker ~]$</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt">From:<span class="apple-converted-space"> </span></span></b><span style="font-size:12.0pt">Andreas Dilger <<a href="mailto:adilger@whamcloud.com"><span style="color:#0563C1">adilger@whamcloud.com</span></a>><br>
<b>Date:<span class="apple-converted-space"> </span></b>Thursday, September 21, 2023 at 2:33 PM<br>
<b>To:<span class="apple-converted-space"> </span></b>"Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.]" <<a href="mailto:darby.vicker-1@nasa.gov"><span style="color:#0563C1">darby.vicker-1@nasa.gov</span></a>><br>
<b>Cc:<span class="apple-converted-space"> </span></b>"<a href="mailto:lustre-discuss@lists.lustre.org"><span style="color:#0563C1">lustre-discuss@lists.lustre.org</span></a>" <<a href="mailto:lustre-discuss@lists.lustre.org"><span style="color:#0563C1">lustre-discuss@lists.lustre.org</span></a>><br>
<b>Subject:<span class="apple-converted-space"> </span></b>[EXTERNAL] Re: [lustre-discuss] Data recovery with lost MDT data<o:p></o:p></span></p>
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<b><span style="font-size:10.0pt;color:black">CAUTION:</span></b><span class="apple-converted-space"><span style="font-size:12.0pt;color:black"> </span></span><span style="font-size:10.0pt;color:black">This email originated from outside of NASA. Please take
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<p class="MsoNormal"><span style="font-size:12.0pt">In the absence of backups, you could try LFSCK to link all of the orphan OST objects into .lustre/lost+found (see lctl-lfsck_start.8 man page for details).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">The data is still in the objects, and they should have UID/GID/PRJID assigned (if used) but they have no filenames. It would be up to you to make e.g. per-user lost+found directories in their home directories
and move the files where they could access them and see if they want to keep or delete the files. <span class="apple-converted-space"> </span><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">How easy/hard this is to do depends on whether the files have any content that can help identify them. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"> <o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:12.0pt">There was a Lustre hackathon project to save the Lustre JobID in a "user.job" xattr on every object, exactly to help identify the provenance of files after the fact (regardless
of whether there is corruption), but it only just landed to master and will be in 2.16. That is cold comfort, but would help in the future. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">Cheers, Andreas<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:12.0pt">On Sep 20, 2023, at 15:34, Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] via lustre-discuss <<a href="mailto:lustre-discuss@lists.lustre.org"><span style="color:#0563C1">lustre-discuss@lists.lustre.org</span></a>>
wrote:<o:p></o:p></span></p>
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<p class="MsoNormal">Hello,<span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">We have recently accidentally deleted some of our MDT data. I think its gone for good but looking for advice to see if there is any way to recover. Thoughts appreciated. <span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">We run two LFS’s on the same set of hardware. We didn’t set out to do this, but it kind of evolved. The original setup was only a single filesystem and was all ZFS – MDT and OST’s. Eventually, we had some small file workflows that we
wanted to get better performance on. To address this, we stood up another filesystem on the same hardware and used a an ldiskfs MDT. However, since were already using ZFS, under the hood the storage device we build the ldisk MDT on comes from ZFS. That
gets presented to the OS as /dev/zd0. We do a nightly backup of the MDT by cloning the ZFS dataset (this creates /dev/zd16, for whatever reason), snapshot the clone, mount that as ldiskfs, tar up the data and then destroy the snapshot and clone. Well, occasionally
this process gets interrupted, leaving the ZFS snapshot and clone hanging around. This is where things go south. Something happens that swaps the clone with the primary dataset. ZFS says you’re working with the primary but its really the clone, and via
versa. This happened about a year ago and we caught it, were able to “zfs promote” to swap them back and move on. More details on the ZFS and this mailing list here. <span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><a href="https://zfsonlinux.topicbox.com/groups/zfs-discuss/Tcb8a3ef663db0031-M5a79e71768b20b2389efc4a4"><span style="color:#0563C1">https://zfsonlinux.topicbox.com/groups/zfs-discuss/Tcb8a3ef663db0031-M5a79e71768b20b2389efc4a4</span></a><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><a href="http://lists.lustre.org/pipermail/lustre-discuss-lustre.org/2022-June/018154.html"><span style="color:#0563C1">http://lists.lustre.org/pipermail/lustre-discuss-lustre.org/2022-June/018154.html</span></a><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">It happened again earlier this week but we didn’t remember to check this and, in an effort to get the backups going again, destroyed what we thought were the snapshot and clone. In reality, we destroyed the primary dataset. Even more
unfortunately, the stale “snapshot” was about 3 months old. This stale snapshot was also preventing our MDT backups from running so we don’t have those to restore from either. (I know, we need better monitoring and alerting on this, we learned that lesson
the hard way. We had it in place after the June 2022 incident, it just wasn’t working properly.) So at the end of the day, the data lives on the OST’s we just can’t access it due to the lost metadata. Is there any chance at data recovery. I don’t think
so but want to explore any options. <span class="apple-converted-space"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">Darby<span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal">_______________________________________________<br>
lustre-discuss mailing list<br>
<a href="mailto:lustre-discuss@lists.lustre.org"><span style="color:#0563C1">lustre-discuss@lists.lustre.org</span></a><br>
<a href="http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org"><span style="color:#0563C1">http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org</span></a><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Cheers, Andreas<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">--<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Andreas Dilger<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Lustre Principal Architect<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Whamcloud<o:p></o:p></span></p>
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