New filesystem: Btrfs!

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

I have an update on my laptop's btrfs root partition conversion via a stage4 tarball and sysresccd. After going through all of the potential disasters on a virtual machine, I made a small cheat sheet on the correct commands to use are and proceeded to perform the procedure on my laptop. It was a complete success.

I have my ssd (OCZSSD2-1S64G) mounted with options compress,ssd_spread,noatime and I am running vanilla-sources-2.6.33-rc4. My general impression is that the system is more responsive.

When doing the conversion, I accidentally mounted root without any options and did not realize until I was rebooting from sysresccd, so I had to do things over again. Uncompressing the tarball felt faster without any mount options, so I am not sure if my choice of mount options is really optimal. I wish I had some filesystem benchmarks I could run to see some actual numbers.

StringCheesian · l33t Joined: 21 Oct 2003 Posts: 887

haarp · Apprentice Joined: 31 Oct 2007 Posts: 286

I had the strangest experience on a fs ever just now. I have a new system with / running on btrfs. Suddenly, the system wouldn't boot anymore. Well, turns out my fstab somehow got modified, replacing my rootfs with the one I used before that (which was ext3). So essentially, this part of the file got replaced by an older version.
What boggles my mind even more though, is that another line, that I edited after the rootfs line, stayed the new version.

Strange, isn't it?

keenblade · Veteran Joined: 03 Oct 2004 Posts: 1038

ToeiRei · Veteran Joined: 03 Jan 2005 Posts: 1113 Location: Austria

btrfs is not the classical filesystem. You need to append rootflags to the kernel command line. or if you use genkernel, it's the real_rootflags parameter to tell it the subvolume to look for the rootfs.
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Shining Arcanine · Veteran Joined: 24 Sep 2009 Posts: 1110

My btrfs root partition is messed up and btrfsck won't fix it:

ToeiRei · Veteran Joined: 03 Jan 2005 Posts: 1113 Location: Austria

could you report this to the btrfs mailing list, Shining Arcanine?
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Shining Arcanine · Veteran Joined: 24 Sep 2009 Posts: 1110

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

Another issue. GCC just died. Apparently, a symbolic link's target changed:

/usr/i686-pc-linux-gnu/gcc-bin/4.4.2/gcc was pointing to /usr/i686-pc-linux-gnu/gcc-bin/4.4.2/i686-pc-linux-g instead of /usr/i686-pc-linux-gnu/gcc-bin/4.4.2/i686-pc-linux-gcc. This happened while was I re-emerging stuff because of the same upgrade that occurred before things went haywire last time. :/

To top things off, firefox now is segfaulting whenever I try to launch. A re-emerge does not help.

I assumed that the issue were my mount options, but it seems that is not the case. I think I will be going back to ext4 and the 2.6.31 kernel.

jormartr · Tux's lil' helper Joined: 02 Jan 2008 Posts: 149

Hi

do you know if nfs works ok on top of btrfs?

I once started portage over nfs on top of btrfs, but that gave me problems reading files.

BlueFusion · Posted: Wed Jan 20, 2010 1:35 am Post subject:

My NFSv3 works fine with a btrfs mount.
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jormartr · Tux's lil' helper Joined: 02 Jan 2008 Posts: 149

BlueFusion · Posted: Wed Jan 20, 2010 3:30 pm Post subject:

Regarding the problem of booting btrfs and requiring the btrfsctl -a command to be ran, is there a way genkernel can be modified to automatically do what needs to be done with the booting kernel/initramfs? Say, there is an option in genkernel.conf to enable or disable that command from being ran upon booting that kernel?

I ask because I was just thinking about it and don't know too much on the kernel initramfs requirements. I know it can be done different ways without genkernel, but just thought that might make things easier for some since I do use genkernel for simplicity's sake.
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EzInKy · Veteran Joined: 11 Oct 2002 Posts: 1734 Location: Kentucky

Update on my earlier post. I decided to try the four disk raid0 setup so I could keep the data on my other four media drives as backup. Overall setting up the array went smooth and fast. This is my df -h output:

Dont Panic · Posted: Fri Jan 22, 2010 2:02 pm Post subject:

Before a multidevice Btrfs arrangement can be properly recognized, you need to run 'btrfsctrl -a'.

So it pretty much requires an initramfs step in your boot procedure, that is modified with a step to run 'btrfsctrl -a' to properly mount a multidevice RAID Btrfs array identified from /etc/fstab.

Probably the only other option is to take the mounting of your multidevice btrfs array out of /etc/fstab, and manually insert the mount command into /etc/init.d/local.

EzInKy · Veteran Joined: 11 Oct 2002 Posts: 1734 Location: Kentucky

kernelOfTruth · Posted: Sun Jan 31, 2010 6:15 pm Post subject:

since I'm starting to use btrfs more seriously is the following the correct way to format a btrfs-partition on a single-partition ?

mkfs.btrfs -d single -m single

the new compress-force option leads to even more space-efficiency !

df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/btrfs 698G 616G 83G 89% /bak (with compress mount-option)
/dev/mapper/btrfs 698G 573G 125G 83% /bak (with compress-force mount-option)
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Hardcore Linux user since 2004

BlueFusion · Posted: Sun Jan 31, 2010 8:49 pm Post subject:

Would the compress-force option work well (speed wise) on a partition containing only large video files? Or would it be better to not use the compression options?
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genstorm · Veteran Joined: 05 Apr 2007 Posts: 1957 Location: Austria

Raw video files are the only scenario where that would be of benefit.
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kernelOfTruth · Posted: Sun Jan 31, 2010 9:08 pm Post subject:

Dont Panic · Posted: Mon Feb 01, 2010 2:27 am Post subject:

The '-o compress' option is supposed to be an optimized compress that would quit trying to compress files that weren't compressing very well.

The recently added '-o compress-force' option will try to compress everything.

One person on the Btrfs Mailing List found '-o compress-force' was actually much faster than '-o compress' on his target files (a database of mostly compressed data).

It will be interesting to get some more data points on speed comparisons for 'compress' and 'compress-force' from other users with different mixes of hardware and data. It's possible that trying to optimize the compression is overly complicating the issue, and many users could be better off just compressing everything (for speed and space).

BlueFusion · Posted: Mon Feb 01, 2010 3:36 am Post subject:

The files are all mkv (x264 mpeg), avi, and the like. None are raw. Right now I have them spread out across several drives running ext4 but btrfs is what I am really looking forward to using for these files.
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Desktop: i7-940 @ 2.93GHz, ASUS P6T Deluxe, 6GB RAM, 2x 160GB, 2x 500GB, 1x 1TB Seagate Barracuda SATA, nVidia 8800GTS 512MB, Hauppage PVR-250

Dont Panic · Posted: Mon Feb 01, 2010 5:08 am Post subject:

BlueFusion · Posted: Mon Feb 01, 2010 5:37 pm Post subject:

I would love to experiment with this data, believe me. My problem is that all my drives are at capacity and don't have the money right now to buy more. I already have to delete old movies I don't want anymore to fit new ones. I have my /usr/portage, /var/tmp/portage, /usr/src, and one other data directory which is backed up occasionally on btrfs so far.

I will see what I can do in experimenting and letting you know the results when I get some free time and space.
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Desktop: i7-940 @ 2.93GHz, ASUS P6T Deluxe, 6GB RAM, 2x 160GB, 2x 500GB, 1x 1TB Seagate Barracuda SATA, nVidia 8800GTS 512MB, Hauppage PVR-250

dufeu · l33t Joined: 30 Aug 2002 Posts: 675 Location: US-FL-EST

I'm seriously thinking of converting some of my filesystems to btfs. I've read through the ext3/ext4 conversion instructions in the btfs wiki. However, I still have a question not answered in the wiki {that I could find} and was hoping someone here could give me some advice on.

How much free space should I have for the conversion to take place? I'm assuming a percentage free since hard drives come in all sizes but an absolute minimum with allowance per 100gigs would also be good.

I'm including the results of my local "df" as a point of reference: