On Mar 05, 2007  15:41 +0100, Harald van Pee wrote:
> I have lustre 1.5.95 running with 3 ost on one machine and and mds and mdt on 
> another.
> 
> Unfortunately these files are created more likely on the ost which is more or 
> less full then on the other 2 (one is less then 60% full).
> 
> Therefore I can not use the full disk space.

This is a bug in the free space management in the older 1.5.x betas that
was fixed recently.  You should try out 1.5.97 and it should prefer to
allocate new files on the least full OST.

One caveat - this decision is made at the time the file is first opened.
If you create a lot of small files, say with OST1 nearly full and OST3
nearly empty then a lot more files will be created on OST3.  If these
files grow slowly over time then it may be that OST1 becomes overly full
(because of the many more files created there) when it was less full.

> The easiest way to do so is if one would be able to give a tune parameter 
> where new files are never created on ost with less then 2 GB free disk space.

That is already done to some extent - when only 0.1% of the filesystem
space is left the OST will not allow new allocations there.  There is
no tunable for this, though almost anyone could implement this quite
easily.  Add a new tunable (obdfilter/lproc_obdfilter.c) and use it for
the check in filter_precreate() (obdfilter/filter.c).

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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