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I am resizing logical volumes on a CentOS server and I have come across an issue where the volumes say that they are 100%, though the "Size" and "Used" columns seem to indicate that there should be more space.

df -h /volume_name
Filesystem  Size   Used  Avail  Use%  Mounted on
/dev/blah   1014G  963G  24M    100%  /volume_name

My resizing process, in case that is contributing to the problem, is:

umount /dev/volume_name
lvresize -L 1014G /dev/volume_name
e2fsck -f /dev/volume_name
resize2fs /dev/volume_name
mount /dev/volume_name /volume_name

Is it normal that there would be so much unused space? When I run e2fsck on the volumes most of them say they have about 2 or 3% non-contiguous space. Could that be contributing to the issue?

Thanks for any help you can give me. I've tried searching for the issue but I may be using the wrong terminology, so even pointing me in the right direction would be much appreciated!

HBruijn
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jdussault
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3 Answers3

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What type of FS is it? In case of ext2/3/4 if you created the FS without specifying reserved blocks, there are 5% reserved blocks by default, that's 50GB in case of 1TB filesystem.

try following:

tune2fs -l /dev/blah |grep -i reserved

These are blocks reserved for the user root - this makes sense for filesystems essential for running the OS, ie rootfs, /var, /tmp etc. but it's seriously contraproductive for /home, /apps etc...

If you want to remove the reservation, type the following:

tune2fs -m0 /dev/blah
cepal67
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  • Would there be any harm for removing reserved blocks for a volume primarily used for file storage (tiffs, xml, etc)? Thanks to everybody for the helpful answers, I wish I had enough street cred on the site to upvote you. :) – jdussault Jun 12 '15 at 16:29
  • the 5% reservation makes sense only on filessytems used by the operating system, as I've mentioned; if your tiffs and XML files reside on such filesystem, then I'd recommend to maybe lower the value (esp. if the filesystem is HUGE - the 5% defautl was set up when filessytems used to be MUCH smaller than nowadays, in hundreds of megabytes)... you can for example set it to 1% (-m1 instead of -m0 in the above command), if the filesystem is 10GB, 1% is still 100MB, should be enough for some emergency running of OS, but better is separate data from operating system, (ie separate /home, /opt/...). – cepal67 Jun 16 '15 at 14:22
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Execute 'dumpe2fs -h /dev/blah |grep -E "lock count"' on the system and take a look at the Block count and Reserved block count. When creating a filesystem 5% of the space is reserved for administrative purposes doing some quick math shows that 5% of 1014G is about 50G. If you want to adjust this you can use the -r and -m options of the tune2fs command to do so.

Dennis Jacobfeuerborn
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By default 5% of the blocks is reserved for the superuser, root, when you create a file-system. You can check the properties of an ext[2-4] file-system with dump2fs.

You can change that percentage with -m option of tune2fs, which is a common thing to do on large volumes.

HBruijn
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