New filesystem: Btrfs!

Shining Arcanine · Veteran Joined: 24 Sep 2009 Posts: 1110

Linux Kernel 2.6.33.4 is out. Although there were no btrfs patches in it, I believe that Linux Kernel 2.6.33.3 did have a btrfs patch. The bug that was fixed seems like a significant issue:

devsk · Posted: Fri May 14, 2010 2:20 am Post subject:

Shining Arcanine · Veteran Joined: 24 Sep 2009 Posts: 1110

devsk · Posted: Fri May 14, 2010 4:15 am Post subject:

echoblack · n00b Joined: 15 May 2010 Posts: 1

Aloha guys,

Nice thread. I'm not a Gentoo user but I have read all your install guides and love the documentation you guys have for "Hardened Gentoo" Super nice setup.... But I'm an Archlinux user because I like Archlinux.

---------------------

Any way, I just got done reading this tread and I think I may know what your problem with file-system corruption may be.

regomodo · Guru Joined: 25 Mar 2008 Posts: 445

skellr · Posted: Fri May 21, 2010 8:41 pm Post subject:

BenderBendingRodriguez · Tux's lil' helper Joined: 19 Feb 2010 Posts: 101

As of now btrfs is my main filesystem for everything (though as always i keep backups on external hard disk

)

My netbook gentoo box sometimes freezes (though not anymore from 2.6.34 gentoo sources) and after the freeze i had to hard reset it and guess what, the system wasn't working fine when booting (lots of boot failures) but i could still log in and reboot as su (if i used Magic Sys Rq combination without logging in and rebooting i had those failures the next boot) and the next boot was completely fine with no lost files (that's copy-on-write magic i suppose) and booting just fine and fast (thought not much faster than ext4 but to be sure i'd have to use bootchart).

BTW here's my fstab

cat /etc/fstab
# /etc/fstab: static file system information.
#
# noatime turns off atimes for increased performance (atimes normally aren't
# needed; notail increases performance of ReiserFS (at the expense of storage
# efficiency). It's safe to drop the noatime options if you want and to
# switch between notail / tail freely.
#
# The root filesystem should have a pass number of either 0 or 1.
# All other filesystems should have a pass number of 0 or greater than 1.
#
# See the manpage fstab(5) for more information.
#

# <fs> <mountpoint> <type> <opts> <dump/pass>

# NOTE: If your BOOT partition is ReiserFS, add the notail option to opts.
/dev/sda1 /boot ext4 noauto,relatime 1 2
/dev/sda5 / btrfs defaults,relatime 0 0
/dev/sda6 /usr btrfs defaults,relatime 1 1
/dev/sda7 /var btrfs defaults,relatime 1 1
/dev/sda8 /tmp btrfs defaults,relatime 1 1
/dev/sda10 /home btrfs defaults,relatime 1 1
/dev/sda9 none swap sw 0 0
#/dev/cdrom /mnt/cdrom auto noauto,ro 0 0
#/dev/fd0 /mnt/floppy auto noauto 0 0

# glibc 2.2 and above expects tmpfs to be mounted at /dev/shm for
# POSIX shared memory (shm_open, shm_unlink).
# (tmpfs is a dynamically expandable/shrinkable ramdisk, and will
# use almost no memory if not populated with files)
shm /dev/shm tmpfs nodev,nosuid 0 0

platojones

regomodo · Guru Joined: 25 Mar 2008 Posts: 445

skellr · Posted: Sat May 22, 2010 12:18 pm Post subject:

The "unknown command" error? Heh, it doesn't seem to make much sense as you have the full path written in your init. What happens when you chroot into the initramfs directory and try to run it?

regomodo · Guru Joined: 25 Mar 2008 Posts: 445

skellr · Posted: Sat May 22, 2010 1:54 pm Post subject:

Yeah it is.

It seems I have the same issue when it's in the sbin directory. Try moving it into bin/.

sbin/ has the same perms as bin/

edit: uid=0 gid=0 should be good enough.

BenderBendingRodriguez · Tux's lil' helper Joined: 19 Feb 2010 Posts: 101

skellr · Posted: Sat May 22, 2010 3:28 pm Post subject:

devsk · Posted: Sat May 22, 2010 7:17 pm Post subject:

Out of blue a whole directory (my portage overlay) is missing in one of my folders. I just noticed it today when I fired 'esearch star' and it said "WARNING: One or more repositories have missing repo_name entries". And I had specifically created that file. I go into the overlay folder and its empty....WOW! WTF! I look at my backup (boy, am I happy to keep them) and the directory structure is same and the overlay folder is there.

This is the second time I am getting eaten by a silent failure for some unknown reason. And I don't know what happened. The scary part is that no warnings or errors were issued by the FS.

Two related events:

1. I had an unclean shutdown yesterday morning but I fscked the FS using livecd and it did not crib about anything.
2. I upgraded from 2.6.24_rc7 to 2.6.34 yesterday evening.

I don't know which one triggered it.

I moved my rootfs to BTRFS a long time ago (much earlier than most folks here) but I am not so sure now.

PS: Before someone starts saying that I deleted the folder by mistake, I log every command I type in a log file with no limits or rotations on it.

platojones · Posted: Sat May 22, 2010 7:25 pm Post subject:

devsk · Posted: Sat May 22, 2010 8:02 pm Post subject:

platojones · Posted: Sat May 22, 2010 8:07 pm Post subject:

devsk · Posted: Sun May 23, 2010 4:15 pm Post subject:

This latest problem does raise a few questions:

1. Do you listen to your 20000 songs collection and watch the 100 movies collection every day? How about every week? How do you know all of them are still there? Not just count but with contents. This is not really btrfs question. It applies to all filesystems.

2. How deep is btrfsck? Why did it not find that the directory checksum for overlay folder is now not same as before because all sub-folders are gone missing now? This means that it overwrote the checksum on newer access (when I went into the folder to find the horror) without checking if it was valid, hence making the new checksum valid. May be there is implicit assumption that if the file system is mounted and online, things can't go wrong (which is bad!!) and current checksum is the "right" checksum. How the heck and when are the problems supposed to be detected using checksums then?

I thought block-level checksum was the answer to these questions but what good is a checksum if its not used and verified against?

Dont Panic · Posted: Sun May 23, 2010 10:45 pm Post subject:

The development of the btrfs file system utilities doesn't seem to be getting as much attention by the developers as the btrfs file system itself.

If I'm reading the Mailing List correctly, the btrfsck utility doesn't currently fix anything. It just reports errors.

As I understand it, the btrfsck utility cannot be run on a mounted file system, even mounted read only.

I see some talk of adding btrfs support to Grub-2. But how will you ever run a start-up fsck of your file system if you can't at least mount it read-only first?

devsk · Posted: Sun May 23, 2010 10:54 pm Post subject:

Dont Panic · Posted: Sun May 23, 2010 11:27 pm Post subject:

It would have been nice to have caught btrfs "in the act" of doing whatever it did.

It sounds like that by the time you found out that directory had issues, the time had already past for gaining insight as to why btrfs was behaving this way.

As to your general question about making sure your data is still there, I've thought about it before also, and don't have a good answer (especially when it comes to big, space-hungry stuff like movies and music). It's nice to have an older back-up around in addition to your fresher backups, because it's easy to make an un-noticed mistake in deleting important data and then propagate that mistake through your backups.