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

[Robin Humble]

On Wed, Jan 16, 2019 at 04:25:25PM +0000, Jason Williams wrote:
>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)

if you are using an older Lustre version (eg. IEEL) then you may have
to re-enable the OST on the MDS to allow deletes to occur on the OST.
then check no new files went there while it was enabled, and possibly
loop and repeat.

the newer ways of disabling file creation on OSTs in recent Lustre
versions don't have this problem.

>- 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?

perhaps check 'lsof' on every client.
if a client has a file open then it can't be deleted.

cheers,
robin