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Re: undelete - xfsrecover'ing deleted files in xfs

To: King Kac <kacperw@xxxxxxxxx>
Subject: Re: undelete - xfsrecover'ing deleted files in xfs
From: Steve Lord <lord@xxxxxxx>
Date: 01 Feb 2002 11:10:00 -0600
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <20020201114711.A5367@comotion>
References: <20020131210325.C966@comotion> <B87F3B30.17EF%gnydick@xxxxxxxxxxxxx> <4.3.2.7.2.20020201142828.037499a0@xxxxxxxxxxxxx> <20020201114711.A5367@comotion>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Fri, 2002-02-01 at 10:47, King Kac wrote:
> [insert amount of random swearwords]
> lost data then, eh? 10K is just a little bit above what I can spend, 
> although I was aware of the option :-) Thanks for the help anyways.
> 
> XFS reuses the freed blocks very fast you say? I'd think that on a 
> striping raid array the blocks wouldn't be as quickly freed... Does 
> this, in essence, mean that if you're stupid and don't back up your 
> data, you lost it forever in xfs?

Unfortunately there is no substitute for backups, because xfs uses
complex on disk structures it is very difficult to get data back 
from a file once you remove it. Sure, if you did not allocate anything
else in the filesystem it is probably still there, but all the
extents which were in the inode have been returned to free space
and the inode no longer contains a record of where they were, the
inode itself is free too, so finding that is a problem too. There is
a reasonable chance that if your files were created at one time 
(rather than being written in little chunks like a log file) that
they were mostly sequential on disk, so finding one part of a file
would usually find you the rest of it too.

Steve

> 
> cheers
>       -Kacper
> 
> On 2002.02.01 08:30 Seth Mos wrote:
> > At 18:19 31-1-2002 -0800, Gabe E. Nydick wrote:
> >> Pay about 10K anywhere up, depending on the size of the drive to 
> >> have it
> >> professionally done.
> > 
> > Try using grep and dd. I have used that before to rescue data. Unless 
> > it's binary data which is really hard to find back.
> > 
> > By the time you reboot the box the data may already have been 
> > overwritten. XFS reuses the just freed blocks very fast.
> > 
> > Cheers
> > 
> > --
> > Seth
> > Every program has two purposes one for which
> > it was written and another for which it wasn't
> > I use the last kind.
> > 
> > 
-- 

Steve Lord                                      voice: +1-651-683-3511
Principal Engineer, Filesystem Software         email: lord@xxxxxxx


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