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List:       lustre-discuss
Subject:    [Lustre-discuss] [wc-discuss] Bad reporting inodes free
From:       andreas.dilger () intel ! com (Dilger, Andreas)
Date:       2012-09-28 12:17:17
Message-ID: 8E55F696-9814-42A3-B123-A73163993D9E () intel ! com
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On 2012-09-28, at 2:15, Johann Lombardi <johann.lombardi at linux.intel.com> wrote:

> On 28 sept. 2012, at 09:03, Alfonso Pardo wrote:
> > If I am need more inodes in my OST, I have a big trouble!, becouse I will need \
> > format all OST in my production storage environment. 
> > Any ideas to increase the inodes number in my OST without formating?
> 
> The number of inodes is decided at mkfs time and can't be changed easily. If your \
> OSTs are on lvm, one option could be to increase the size of the logical volumes \
> and resize the backend ldiskfs filesystems. However, i'm not sure someone has ever \
> tried this with ldiskfs/lustre, so i would not do this on a production filesystem \
> w/o some testing first.

Right. It would be possible to use "lfs_migrate" to empty an OST, then reformat with \
more inodes, then migrate another OST's files to the newly formatted OST, repeat. \
However, I think that would be pointless, see below. 

> In any case, i think the issue here is that you seem to have a default stripe count \
> of -1. That's why you are limited by the number of inodes available on one single \
> OST. You should still be able to create ~1.250M x 18 = 22.5M 1-stripe files.

That is my thought as well - the default file striping is too large. What is the \
average file size (total space used / mdt used inode count)?  Having many stripes on \
small files (below tens of MB per stripe) is actuall bad for performance.

If this is the case (many stripes on small files) then it is possible to use \
lfs_migrate to change the striping of the files incrementally (caveat that it is only \
safe for files known not to be in use). 

As Johann mentioned, there are still over 20M OST inodes free, and if the existing \
files were converted to 1-stripe files there would be about 330M OST inodes free.

Cheers, Andreas


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