ReiserFS's stability is not actually quite good [LWN.net]

ReiserFS's stability is not actually quite good

Posted Apr 27, 2006 13:36 UTC (Thu) by dmantione (guest, #4640)
In reply to: ReiserFS's stability is not actually quite good by nix
Parent article: Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration)

<I>I had major disk corruption on ext3 once, but when your disk drive
decides to put blocks somewhere other than where the filesystem asked for
them to go, you have little option but to get a new disk and restore from
backup, really...</I>

Yes, you would prefer to restore from backup.

However, if you did not backup the data, either due to cost/benefit
calculation (i.e. I wouldn't backup my mp3 collection but would try to
restore it) or due to stupidity, you have exactly a situation where
Reiserfs would have saved your data.

In such a situation the reiserfsck --rebuild-tree option, which you
bashed in an earlier post of you is invaluable. The procedure for
recovery is as follows:

* Connect a new disk with the same size or larger as the failing disk.
* Boot from a rescue CD.
* Do not enable any LVM arrays.
* dd the old disk over the new one. If it fails due to a bad sector, skip
some sectors and continue from that place using the right command line
options.
* Remove the old disk.
* If the disk was in an LVM array, enable it. LVM will detect the new
disk as if it was the old one.
* Reiserfsck the filesystem with --rebuild-tree.

Your actual data loss depends on the severity of the corruption. I've had
this experience once, with about 12000 bad sectors, in which I lost 700
mb out of 1,2 GB of data. Some files did appear in /lost+found.

It is easy to bash the --rebuild-tree option because it is not 100% safe
due to possible reiserfs images on the disk. You don't need to use it, a
lot of corruptions can be repaired without it. If you really need it, and
your actual data is intact, the option almost guarantees the data can be
retreived from the disk intact.

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ReiserFS's stability is not actually quite good

Posted Apr 27, 2006 23:43 UTC (Thu) by dlang (✭ supporter ✭, #313) [Link]

so you are saying that reiserfs knows better then the admin. personally I won't use software that decides it knows what I should do better then I do (good defaults are one thing, engineering the product to not allow for choice in another)

you are overlooking the fatal flaw with rebuild tree, namely it grabs ALL blocks that look like they are reiserfs tree blocks, unfortunantly with loop mounted filesystems you can have many filesystems on one partition (the main one, and then the ones that are images in files), rebuild tree will try to combine them all.

ReiserFS's stability is not actually quite good

Posted Apr 29, 2006 11:00 UTC (Sat) by nix (subscriber, #2304) [Link]

I can't imagine *any* filesystem saving my data if the disk has been placing blocks in the wrong place for five minutes during intense writes (which was what happened here).

reiserfsck is not going to be any luckier here than any other repair tool because the data is *overwritten*. --rebuild-tree is not magical (any tool which can be misled by the *contents of files* deserves a rather different word to describe it).