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Related tags: filesystems, misc, tools.

Sanity testing drives

Thursday, 12 August 2010

Recently I came across a situation where moving a lot of data around on a machine with a 3Ware RAID card ultimately killed the machine.

To test the hardware in advance for this requires a test of both:

  • The individual drives, which make up the RAID array
  • The filesystem which is layered upon the top of it.

The former can be done with badblocks, etc. The latter requires a simple tool to create a bunch of huge files with "random" contents, then later verify they have the contents you expected.

With that in mind:

dt --files=1000  --size=100M [--no-delete|--delete]

This:

  • Creates, in turn, 1000 files.
  • Each created file will be 100Mb long.
  • Each created file will have random contents written to it, and be closed.
  • Once closed the file will be re-opened and the MD5sum computed
    • Both in my code and by calling /usr/bin/md5sum.
    • If these sums mis-match, indicating a data-error, we abort.
  • Otherwise we delete the file and move on.

Adding "--no-delete" and "--files=100000" allows you to continue testing until your drive is full and you've tested every part of the filesystem.

Trivial toy, or possibly useful to sanity-check a filesystem? You decide. Or just:

hg clone http://dt.repository.steve.org.uk/

(dt == disk test)

ObQuote: "Stand back boy! This calls for divine intervention! " - "Brain Dead"

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