File System Testing – How to Corrupt a File System for Testing Purposes

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I am going to be testing 'xfs_repair' on some large file systems ( around 50 TB ) as in the past the memory usage is high. While I could test the program only on file systems which were correct it would be good to test them on a corrupt system.

So what would be the best way to corrupt a file system. Extra credit if the method repeatedly gives the same corruption every time….

To give people an idea of what I mean in 2006 ish

"To successfully check or run repair on a multi-terabyte filesystem, you need:

  • a 64bit machine
  • a 64bit xfs _ repair/xfs _ check binary
  • ~2GB RAM per terabyte of filesystem
  • 100-200MB of RAM per million inodes in the filesystem.

xfs_repair will usually use less memory than this, but these numbers give you a ballpark figure for what a large filesystem that is > 80% full can require to repair.

FWIW, last time this came up internally, the 29TB filesystem in question took ~75GB of RAM+swap to repair."

Best Answer

xfs_db has an option blocktrash which

Trash randomly selected filesystem metadata blocks. Trashing occurs to randomly selected bits in the chosen blocks. This command is available only in debugging versions of xfs_db. It is useful for testing xfs_repair(8) and xfs_check(8).

For example

xfs_db -x -c blockget -c "blocktrash -s 512109 -n 1000" /dev/xfstest/testfs

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