How to damage a XFS-Filesystem?

Hi,

I have the following scenario:

A file server with a 10 TB large xfs file system running on a RAID6 SATA array, the server has 16 GB of memory. I want to test how long it would take to run xfs_repair on it and if the amount of memory is enough for that.

Thus I think I would need to:

(1) Fill the disk with files
(2) Damage the file sytem
(3) Run xfs_repair

My questions:

(1) Is there a nice tool which fills up a disk? I.e. I want to write files with varying size and want to be able to check the validity (md5,sha1...) of the files before and after the damage. I don't know if it matters, but the number of entries per directory should also vary greatly ;)

(2) I don't know if xfs_repair cares if the file system was damaged or not. If it uses the same amount of time and memory on a fully intact file system, I guess I don't have a question anymore. Otherwise: How can a damage a xfs file system to make the job harder for xfs_repair. I guess a simple dd if=/dev/random of=/dev/sdb1 with some offsets will not be very effective, right?

(3) Anything else I need to be aware of?

Thanks for your patience (and yes, I have tried the archives for answers)

Cheers

Carsten

It depends on how fast the IO is and also how many files there are.

If you have a small number of really large files it's fairly fast, if you have a large number of really small files (ie. email maildir) then it tends to be much slower.

xfs_repair will run without having to damage the filesystem (though if/when damaged it will probably be a little slower).

Google for fsfuzzer.

If it misses the metadata, xfs_repair won't even notice. If you whack large chunks of metadata you might see considerable data loss.