[lustre-discuss] ZFS not freeing disk space

Thomas Roth t.roth at gsi.de
Wed Aug 10 10:57:45 PDT 2016

Hi all,

one of our ((Lustre 2.5.3, ZFS 0.6.3) OSTs got filled up to >90%, so I deactivated it and am now 
migrating files off of that OST.

Checking the list of files I am currently using, I can verify that the migration is working: Lustre 
tells me that the top of the list is already on some other OSTs, the bottom of the list still resides 
on the OST in question.

But when I do either 'lfs df' or 'df' on the OSS, and don't see any change in terms of bytes, while 
the migrated files already sum up to several GB.

Is this a special feature of ZFS, or just a symptom of a broken OST?

I think I have seen this behavior before, and the "df" result shrank to an expected value after the 
server had been rebooted. In that case, this seems more like a too persistent caching effect -?


Thomas Roth
Department: Informationstechnologie
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