Question about file system checks

[Ivan Voras]

Danny Pansters wrote:

> Generally I can say that with freebsd even if you pull the plug and then let 
> it reboot and do the automatical background fsck you'll likely loose only 
> that one file you might have been editing while (or just before) you 
> unplugged the box.

Stress testing I've done suggests otherwise :) I've literally repeatedly 
pulled the plug of a server in a controlled environment, and with a 
network logging of (a high load of) file system operations. My results 
show that UFS+SU and ZFS on FreeBSD loose *the most* files (and in case 
of UFS+SU especially directories), than any of: jfs, xfs, reiser3 (on 
Linux 2.6.22) and NTFS (on Windows 2003 Server). ext3 is somewhat 
similar to UFS+SU, though about 30% better at not loosing files.

Some other notes from this proceeding:

1. UFS+gjournal looses the least, but it's also the slowest.
2. UFS+SU had no truncated files or files of unexpected length 
(apparently it just looses the file that would end up in this state)
3. XFS and JFS end up with a *huge* number of files that are truncated 
or of unexpected length (40%-50%!)
4. In no case has any of the above file systems gone completely 
corrupted or lost any of the files/directories not being updated.
5. ZFS on FreeBSD was the fastest, in the sense of creating the most 
files during this benchmark (though speed was not the target for this 
benchmark so this is a low-quality observation), closely followed by JFS 
and XFS.
6. ZFS crashed the kernel at least once.

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