Hi Torsten,
There is no reason to suspect that space usage on the MDT will be the
same as the average space usage on the OSTs.
Your MDT is storing the metadata about _all_ of the files in your Lustre
filesystem. You can think of this metadata as a whole bunch of
zero-length files with some extended attributes, because under the
covers that is basically what the MDT is storing.
So space usage on the MDT will be directly proportional to the total
number of files in your Lustre filesystem. The size of those files
doesn't really matter much, because the contents of the files are stored
on the OSTs.
So your issue is that, for your filesystem, on average your files are
too small to allow filling your OSTs. Some possible solutions are:
* Increase the size of your MDT
* Encourage/require your users to start using larger average file sizes
Granted, neither approach is terribly easy.
I think that you can pretty safely ignore the changelogs suggestion.
Chris
On 10/16/2015 07:31 AM, Torsten Harenberg wrote:
Am 16.10.2015 um 16:01 schrieb Ben Evans:
Looks like you¹ve got some really large changelogs built up. Did you have
robin hood, or some other consumer running at some point that has since
stalled?
Don't think so, as I never heard about "Robin Hood" in the context of
Lustre.
The setup is pretty simple, devices were created with
mkfs.lustre --fsname=lustre --mgs --mdt --backfstype=ext4
--failnode=132.195.124.201@tcp --verbose /dev/mapper/MGTMDT
and
mkfs.lustre --fsname=lustre --ost --backfstype=ext4
--failnode=132.195.124.204@tcp --mgsnode=132.195.124.202@tcp
--mgsnode=132.195.124.201@tcp --verbose /dev/mapper/OST0000
respectively
The only "add-on" we have is quota support. Back in 2.1.5 that was
enabled with:
lfs quotacheck –ug /lustre
lfs quotaon /lustre
The file system is mounted on about 200 nodes and accessed by cluster
users.
Best regards,
Torsten
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