[Lustre-discuss] inode tuning on shared mdt/mgs

Aaron Everett aeverett at forteds.com
Tue Jul 5 11:16:10 PDT 2011

Thank you both for the explanation. I have spent the morning populating our
Lustre file system with test data, and monitoring the inode usage. Having
reformatted with --mkfsoptions="-i 1536" I'm seeing roughly 8M IUsed for
every 1M IFree decrease. If the ratio holds, this will meet my needs.


On Sat, Jul 2, 2011 at 10:54 AM, Kevin Van Maren <kevin.van.maren at oracle.com
> wrote:

> Andreas Dilger wrote:
>  On 2011-07-01, at 12:03 PM, Aaron Everett <aeverett at forteds.com <mailto:
>> aeverett at forteds.com>> wrote:
>>> I'm trying to increase the number of inodes available on our shared
>>> mdt/mgs. I've tried reformatting using the following:
>>>  mkfs.lustre --fsname fdfs --mdt --mgs --mkfsoptions="-i 2048" --reformat
>>> /dev/sdb
>>> The number of inodes actually decreased when I specified -i 2048 vs.
>>> leaving the number at default.
>> This os a bit of an anomaly in how 1.8 reports the inode count. You
>> actually do have more inodes on the MDS, but because the MDS might need to
>> use an external block to store the striping layout, it limits the returned
>> inode count to the worst case usage. As the filesystem fills and these
>> external blck
> [trying to complete his sentence:]
> are not used, the free inode count keeps reporting the same number of free
> inodes, as the number of used inodes goes up.
> It is pretty weird, but it was doing the same thing in v1.6
>  We have a large number of smaller files, and we're nearing our inode limit
>>> on our mdt/mgs. I'm trying to find a solution before simply expanding the
>>> RAID on the server. Since there is plenty of disk space, changing the bytes
>>> per inode seemed like a simple solution.
>>> From the docs:
>>> Alternately, if you are specifying an absolute number of inodes, use
>>> the-N <number of inodes> option. You should not specify the -i option with
>>> an inode ratio below one inode per 1024 bytes in order to avoid
>>> unintentional mistakes. Instead, use the -N option.
>>> What is the format of the -N flag, and how should I calculate the number
>>> to use? Thanks for your help!
>>> Aaron
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