OK.

On Wed, Feb 22, 2012 at 8:58 PM, Duncan [off-list ref] wrote:

qasdfgtyuiop posted on Tue, 21 Feb 2012 20:11:06 +0800 as excerpted:

quoted

I'm using GNU/linux with btrfs root. My filesystem is created with
command "mkfs.btrfs /dev/sda" . =A0Today I'm trying to install Micro=

soft

quoted

Windows 7 on /dev/sdb , a 16GB esata ssd. =A0After the installation,=

 I

quoted

found that Windows create a "hidden" NTFS partition called "System
Reserved" on the first 100MB of my /dev/sda and that my btrfs filesy=

stem

quoted

was lost! =A0I have searched google for help but I got no useful
information. =A0Is there any data recovery tools?

The btrfs kernel option says:

Btrfs filesystem (EXPERIMENTAL) Unstable disk format

Its description says in part:

Btrfs is highly experimental, and THE DISK FORMAT IS NOT YET FINALIZE=

D.

You should say N here unless you are interested in testing Btrfs with=

 non-

critical data. [...] If unsure, say N.

The front page and getting started pages of the wiki (see URL below)
also heavily emphasize the development aspect and backups, and the so=

urce

code section has this to say:

Warning, Btrfs evolves very quickly do not test it unless:

=A0 =A0You have good backups and you have tested the restore capabili=

ty

=A0 =A0You have a backup installation that you can switch to when
=A0 =A0 =A0 =A0something breaks
=A0 =A0You are willing to report any issues you find
=A0 =A0You can apply patches and compile the latest btrfs code agains=

t your

=A0 =A0 =A0 =A0kernel (quite easy with git and dkms, see below)
=A0 =A0You acknowledge that btrfs may eat your data
=A0 =A0Backups! Backups! Backups!


Given all that, any data you store on btrfs is by definition not part=

icularly

important, either because you have it backed up in a more stable form=

at

elsewhere (which might be the net, or local), or because the data rea=

lly

/isn't/ particularly important to you in the first place, or you'd ha=

ve

made and tested backups (naturally, always test recovery from your ba=

ckups,

as an untested backup is worse than none, since it's likely to give y=

ou

a false sense of security) before putting it on the after all still
experimental and under heavy development btrfs in the first place.

Thus, you shouldn't need to worry about a data recovery tool, since
you can either simply restore from backups (which since you tested
recovery, you're already familiar with the recovery procedures),
or the data was simply garbage you were using for testing and didn't
care about losing anyway.


Never-the-less, yes, there's a recovery tool, naturally experimental
just like the filesystem itself at this point, but there is one. =A0T=

esting

and suggestions for improvements, especially with patches, will be
welcomed.

It seems you need to read up on the wiki, which covers this among oth=

er

things. =A0There's an older version on btrfs.wiki.kernel.org, but tha=

t's

not updated ATM due to restrictions in place since the kernel.org
breakin some months ago. =A0The "temporary" (but six months and count=

ing,

I believe) replacement is at btrfs.ipv5.de:

http://btrfs.ipv5.de/index.php?title=3DMain_Page

The restore and find-root commands from btrfs-progs are specifically
covered on this page:

http://btrfs.ipv5.de/index.php?title=3DRestore

If you wish to try a newer copy of btrfs-progs (after all, it's all
still in development, and bugs are fixed all the time), you'll also w=

ant

to read:

http://btrfs.ipv5.de/index.php?title=3DGetting_started#Compiling_Btrf=

s_from_sources

--
Duncan - List replies preferred. =A0 No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master." =A0Richard Stallman

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