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ak47gen
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PostPosted: Mon Jan 05, 2009 8:43 pm    Post subject: Is it possible to boot to a BTRFS Reply with quote

As of now i uses ext2 for /boot and an mdadm raid 0 of ext3 for /
The issues i am having is how to you pass on to the kernel boot capablities for a raid root drive that is using btrfs.
I am using zen kernel with build in 0.16 btrfs. And i keep getting a unknown mountable volume.

If this isn't possible let me know, but if it is i can give you more info if you can help me trouble shoot it.[/code]
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nixnut
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PostPosted: Tue Jan 06, 2009 6:38 pm    Post subject: Reply with quote

Moved from Other Things Gentoo to Unsupported Software.
Unsupported stuff, so moved here
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buuban
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PostPosted: Tue Jan 06, 2009 10:12 pm    Post subject: Reply with quote

BTRFS is currently unstable. Even those stable releases carry many issues (I was testing 0.16 for a while). The disk format keeps changing and BTRFS was not exactly the fastest on my system. For a day to day work this is really not what you're looking for. I suggest trying Reiser4 or some other, more stable fs.
BTRFS is good for testing on a small partition with no meaningful data, not for root.
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ToeiRei
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PostPosted: Wed Jan 07, 2009 7:39 am    Post subject: Reply with quote

Hello ak47gen,

Yes, it is possible to boot from btrfs volumes - there are people from the development team who already did so. BUT: you should compile btrfs into the kernel to be able to do so. As btrfs isn't in the main tree (but we're on the way to do so!), you need to get the proper kernel sources which can be checked out from the repository using git

Code:
git clone git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable.git


good luck and may tux bless you.

Rei
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buuban
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PostPosted: Wed Jan 07, 2009 8:11 am    Post subject: Reply with quote

I thought zen-sources have both btrfs-stable and unstable from Your git.
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ToeiRei
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PostPosted: Wed Jan 07, 2009 8:28 am    Post subject: Reply with quote

Honestly, I don't trust zen-sources in combination with btrfs, as btrfs can fuck up the filesystem by itself without the help of any other patches.
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ak47gen
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PostPosted: Fri Jan 09, 2009 1:51 pm    Post subject: Reply with quote

Lets say that the zen isn't the issue why its not booting, how do i mount root as the raided btrfs.

As of now I have it as /dev/sda1. Before i had it /dev/md0. Since btrfs doesn't create one file for the array, but instead all the partitions have its own way of detecting, am I doing this right?

When I get back home later I will try to use the btrfs kernel instead of zen, I was having issues with my USB at boot anyway with zen.
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ToeiRei
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PostPosted: Sat Jan 10, 2009 7:04 pm    Post subject: Reply with quote

btrfs assembles a raid by mounting. So it automatically puts it together. Btw - btrfs made it into the mainline kernel.
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Dont Panic
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PostPosted: Sat Jan 10, 2009 8:15 pm    Post subject: Reply with quote

When they say "btrfs made it into the mainline kernel", where does that mean it will start showing up?

Will we only see it in >=2.6.29 kernel versions?

Or can we expect to see it in updates to <=2.6.28?

Or am I just totally confused as to the implecations? :)
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StringCheesian
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PostPosted: Sat Jan 10, 2009 8:29 pm    Post subject: Reply with quote

Dont Panic wrote:
When they say "btrfs made it into the mainline kernel", where does that mean it will start showing up?

Will we only see it in >=2.6.29 kernel versions?

Yes, 2.6.29.

Article: http://www.phoronix.com/vr.php?view=Njk4Mw
Thread: http://www.phoronix.com/forums/showthread.php?t=14799
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PostPosted: Sun Jan 11, 2009 1:39 am    Post subject: Reply with quote

And 2.6.29-r1 was just released, so you could run that! If you dare.
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gimpel
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PostPosted: Sun Jan 11, 2009 2:07 am    Post subject: Reply with quote

If you have / as a subvolume, it might get tricky to boot from that. Otherwise it shouldn't be an issue. Just like with any other FS.

Welcome BTRFS to mainline! That's really great news for the Linux FS world! I already use it for my storage. / is still ext3 here, and /usr ist still reiser4. If BTRFS' transparent compression performs as well as reiser4's does, I might start thinking of switching.
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PostPosted: Mon Jan 12, 2009 3:21 am    Post subject: Reply with quote

boot from btrfs root is easy, just add kernel options like this:
root=/dev/sda2 rootfstype=btrfs rootflags=compress,subvol=gentoo,device=/dev/sdb1,device=/dev/sdc1
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gimpel
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PostPosted: Mon Jan 12, 2009 7:09 pm    Post subject: Reply with quote

s4e8 wrote:
boot from btrfs root is easy, just add kernel options like this:
root=/dev/sda2 rootfstype=btrfs rootflags=compress,subvol=gentoo,device=/dev/sdb1,device=/dev/sdc1

Wow, easy indeed!

The two devices sdb1 and sdc1 mean a raid1 setup for /, right?
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buuban
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PostPosted: Mon Jan 12, 2009 7:59 pm    Post subject: Reply with quote

AFAIR you can use two devices as one volume without LVM/RAID setup with BTRFS just like with ZFS. I'm not 100% sure though, never tried it.
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gimpel
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PostPosted: Mon Jan 12, 2009 10:41 pm    Post subject: Reply with quote

buuban wrote:
AFAIR you can use two devices as one volume without LVM/RAID setup with BTRFS just like with ZFS. I'm not 100% sure though, never tried it.

Yeah that's what i meant with "raid1", a BTRFS data raid1.
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Naib
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PostPosted: Tue Jan 13, 2009 8:47 am    Post subject: Reply with quote

yes you can

http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices

you can add at anytime another disk to the pool (just like with zfs)

I am actually tempted to use btrfs as the main storage fs on a new server build next month
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