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The df /data command is not showing the exact disk usage information.

This is what I get as output:

Filesystem  1K-blocks  Used     Available Use%   Mounted on /dev/mapper/VolGroup-lvol0  

            41153856   2099892  36956812  6%     /data

Actually when I issued lvdisplay this partition shows 40GB. But when I converted this KiB or KB into GiB it’s not giving the correct output. And may I know inode size is included, also just tell me is there any reserved spaces are there for a partition.

I also checked the inode size using tune2fs -l command for /data partition and it's showing inode size = 256 bytes.

The Reserved Block Count is 524288.

The actual difference is (40 GiB) 41943040 KiB - 41153856 (output from "#df /data") is equal to 789184 KiB. Please tell me why this much difference.

Giacomo1968
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karthikeyan vijayan
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  • I'd bet this answers your question. Basically the number of available blocks is not the same as the total volume size due to some overhead in the filesystem. – zagrimsan Sep 19 '15 at 06:01

1 Answers1

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All filesystems have overhead; which comes of the need to keep track of:

  • where data is stored,
  • attributes (read-only, access rights, ...)
  • filenames,
  • folders
  • and their relationships
  • and how to find them QUICKLY (hashes)
  • ... (more, e.g. journaling, depending on filesystem)

... on top of the data that you store on the partition/disk/volume/...

The posting link provided by zagrimsan (comment on the Q) has a lot of detail on the above.

Also consider deleted files that are still open, see here

Community
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Hannu
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