Reiser just bit me! (was: Comparison of filesystems)

[Digby Tarvin <digbyt@acm.org>]

> >
> >P.S. to include something relevent to the original thread, I have
> >use both Reiserfs and Ext3, and have never found enough performance
> >or reliability difference to worry about - so for me the main
> >advantges of each are:
> >  ext3     - more complere set of tools, such as dump/restore
> 
> IMO, this is the single most important issue with any
> of these file systems. They are all good it seems. But the
> additional support varies widely.

After my earlier comment above, I have just been bitten by a Reiserfs
bug which I think gives me an even better reason to lean towards ext3
at the moment...

I originally mis-reported this as a dump/restore problem, because I was
unable to restore successfully from archive files larger than 2GB, but
on further investigation today....

1. scenario
	digbyt@fujitsu# mount 
    ...
	/dev/hda14 on /home type ext3 (rw)
	/dev/hda13 on /usr/local type ext3 (rw)
	/dev/sda2 on /mnt/sda2 type reiserfs (rw)
	/dev/sda3 on /mnt/sda3 type ext3 (rw)
	digbyt@fujitsu# ls -l ~digbyt/testfile
	-rw-r--r-- 1 root root 2502686720 2006-04-28 17:03 /home/digbyt/testfile

2. copy big file to reiser filesystem on USB drive

	digbyt@fujitsu# dd if=~digbyt/testfile of=/mnt/sda2/testfile
	4888060+0 records in
	4888060+0 records out
	digbyt@fujitsu# ls -l /mnt/sda2/testfile
	-rw-r--r-- 1 root root 2502686720 2006-04-28 19:48 /mnt/sda2/testfile

3. all looks ok, copy from reiser back to ext3 partion on ide disk:
	2502686720 bytes (2.5 GB) copied, 219.419 seconds, 11.4 MB/s
	digbyt@fujitsu# dd if=/mnt/sda2/testfile of=testfile
	dd: reading `/mnt/sda2/testfile': Input/output error
	4194304+0 records in
	4194304+0 records out
	2147483648 bytes (2.1 GB) copied, 125.64 seconds, 17.1 MB/s

3. can't read back from reiser, try copying to an ext3 partition on USB:
	digbyt@fujitsu# dd if=~digbyt/testfile of=/mnt/sda3/testfile
	4888060+0 records in
	4888060+0 records out
	2502686720 bytes (2.5 GB) copied, 225.598 seconds, 11.1 MB/s

4. Now retry copy from USB to IDE partitions
	digbyt@fujitsu# dd if=/mnt/sda3/testfile of=testfile2
	4888060+0 records in
	4888060+0 records out
	2502686720 bytes (2.5 GB) copied, 156.104 seconds, 16.0 MB/s

5. Conclusion - for some reason the reiser filesystem allows me to
   write files longer than 2GB, but will not let me read back past
   2GB into the file:

	digbyt@fujitsu# ls -l
	total 4545628
	-rw-r--r-- 1 root root 2147483648 2006-04-28 19:54 testfile
	-rw-r--r-- 1 root root 2502686720 2006-04-28 20:08 testfile2
	digbyt@fujitsu# dc
	16o
	2147483648p
	80000000

This test was done on Debian Etch. The reiserfs on the USB drive was
formatted on another older system, and was reported as
	reiserfs format "3.5" with standard journal
vs the "3.6" format created by current Debian tools, and the problem
does not seem to exist on the "3.6" format filesytems...

A limit on filesize is not too serious an issue, but allowing me to
write data which cannot later be read without generating any form of
warning is a serious driver deficiency, even for media which is
removeable and was formatted elsewhere or some time ago...

If I hadn't checked the backups before blowing away the old filesytem
it could have been very ugly...

Comparisons of efficiency are rather moot unless the items concerned
can be relied upon to function correctly. 

As they say  "I can make it go as fast as you like if it doesn't have
to be correct"...

Regards,
DigbyT
-- 
Digby R. S. Tarvin                                          digbyt(at)digbyt.com
http://www.digbyt.com