[lustre-discuss] Migrating files doesn't free space on the OST

Chad DeWitt ccdewitt at uncc.edu
Thu Jan 17 12:07:41 PST 2019


Hi Jason,

I do not know if this will help you or not, but I had a situation in 2.8.0
where an OST filled up and I marked it as disabled on the MDS:

lctl dl | grep osc
...Grab the *device_id* of the full OST and then deactivate it...
lctl --device *device_id* deactivate

IIRC, this allowed the data to be read, but deletes were not processed.
When I re-activated the OST, then the deletes were processed and space
started clearing.  I think you stated you had the OST deactivated.  If you
still do, try to reactive it.

lctl --device *device_id* activate

Once you reactivate the OST, the deletes will start processing within 10 -
30 seconds...  Just use lfs df -h to watch...

-cd


------------------------------------------------------------

Chad DeWitt, CISSP

UNC Charlotte *| *ITS – University Research Computing

9201 University City Blvd. *| *Charlotte, NC 28223

ccdewitt at uncc.edu *| *www.uncc.edu

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On Thu, Jan 17, 2019 at 2:38 PM Jason Williams <jasonw at jhu.edu> wrote:

> Hello Alexander,
>
>
> Thank you for your reply.
>
> - We are not using zfs, it's an LDISKFS backing store, so no snapshots.
>
> - I have re-run lfs getstripe to make sure the file is indeed moving
>
> - I just looked for lfsck but I don't seem to have it.  We are running
> 2.10.4 so I don't know what version that appeared in.
>
> - I will try to have a look into the jobstats and see what I can find, but
> I made sure the files I moved were not in use when I moved them.
>
>
>
> --
> Jason Williams
> Assistant Director
> Systems and Data Center Operations.
> Maryland Advanced Research Computing Center (MARCC)
> Johns Hopkins University
> jasonw at jhu.edu
>
>
>
> ------------------------------
> *From:* Alexander I Kulyavtsev <aik at fnal.gov>
> *Sent:* Thursday, January 17, 2019 12:56 PM
> *To:* Jason Williams; lustre-discuss at lists.lustre.org
> *Subject:* Re: Migrating files doesn't free space on the OST
>
>
> - you can re-run command to find files residing on ost to see if files are
> new or old.
>
> - zfs may have snapshots if you ever did snapshots; it takes space.
>
> - removing data or snapshots has some lag to release the blocks (tens of
> minutes) but I guess that is completed by now.
>
> - there are can be orphan objects on OST if you had crashes. On older
> lustre versions if the ost was emptied out you can mount underlying fs as
> ext4 or zfs; set mount to readonly and browse ost objects - you may see if
> there are some orphan objects left. On newer lustre releases you probably
> can run lfsck (lustre scanner).
>
> - to find what hosts / jobs currently writing to lustre you may enable
> lustre jobstats; clear counters and parse stats files in /proc . There was
> xltop tool on github for older versions of lustre not having implemented
> jobstats but it was not updated for a while.
>
> - depending on lustre version you have the implementation of lfs migrate
> is different. The older version copied file with other name to other ost,
> renamed files and removed old file. If migration done on file open for
> write by application the data will not be released until file closed (and
> data in new file are wrong). Recent implementation of migrate does swap of
> the file objects with file layout lock taken. I can not tell if it is safe
> for active write.
>
> - not releasing space can be a bug - did you check jira on whamcloud? What
> version of lustre do you have? Is it ldiskfs or zfs based? zfs version?
>
>
> Alex.
>
>
> ------------------------------
> *From:* lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on
> behalf of Jason Williams <jasonw at jhu.edu>
> *Sent:* Wednesday, January 16, 2019 10:25 AM
> *To:* lustre-discuss at lists.lustre.org
> *Subject:* [lustre-discuss] Migrating files doesn't free space on the OST
>
>
> I am trying to migrate files I know are not in use off of the full OST
> that I have using lfs migrate.  I have verified up and down that the files
> I am moving are on that OST and that after the migrate lfs getstripe indeed
> shows they are no longer on that OST since it's disabled in the MDS.
>
>
> The problem is, the used space on the OST is not going down.
>
>
> I see one of at least two issues:
>
> - the OST is just not freeing the space for some reason or another ( I
> don't know)
>
> - Or someone is writing to existing files just as fast as I am clearing
> the data (possible, but kind of hard to find)
>
>
> Is there possibly something else I am missing? Also, does anyone know a
> good way to see if some client is writing to that OST and determine who it
> is if it's more probable that that is what is going on?
>
>
>
> --
> Jason Williams
> Assistant Director
> Systems and Data Center Operations.
> Maryland Advanced Research Computing Center (MARCC)
> Johns Hopkins University
> jasonw at jhu.edu
>
> _______________________________________________
> lustre-discuss mailing list
> lustre-discuss at lists.lustre.org
> http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
>
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