In-place conversion of ext4 on RAID5 to btrfs RAID5

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    • In-place conversion of ext4 on RAID5 to btrfs RAID5

      Hey everyone,

      I'm fairly new to OMV and NAS in general and have a question concerning my storage setup.

      I read quite a few things about btrfs recently and like the checksumming, CoW, and dynamic changing of RAID levels and array size. Afaik the next version of OMV in the not too distant future will support btrfs, since it will be based on wheezy. So once the new version is out I'd like to change my filesystem to btrfs using RAID5. I'd like to do the conversion in place, since I don't have that many spare disks and already know that ext4 can be converted to btrfs.

      My question is how I should set up my storage now to make this possible. Am I right that I cannot use a RAID setup until then because btrfs does RAID inside the fs while the RAID currently offered by OMV is on a lower level? And running btrfs on top of it would get me checksumming but not automatic repair since btrfs would not not know of the redundant copy? And I also could not use btrfs' dynamic RAID features since it would only see the large RAID disk presented to it by OMV and not the individual drives and I'd have no change of changing that other than breaking the RAID and losing all data?

      Thank you for your help :)
    • Re: In-place conversion of ext4 on RAID5 to btrfs RAID5

      You can probably convert ext4 to btrfs that is still on top of mdadm software raid but I doubt you can convert ext4 on top of mdadm software raid to btrfs raid. I know you said you don't have the spare disks but I wouldn't want to try any of this without a backup.

      From what I can tell, I doubt OMV will have support for btrfs raid 5 since it requires the backports kernel (and backports btrfs-tools). A ZFS plugin is being worked on.
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    • Re: In-place conversion of ext4 on RAID5 to btrfs RAID5

      Don't get your hopes to high with BTRFS. Even in Kernel 3.13 its still considered experimental!

      Greetings
      David
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    • Hi Folks,

      Did anyone give it a try since BTRFS is now stable?

      Right now Im in the middel of an btrfs-convert TEST EXT3 FS with 4x 2TB Raid5 MD devices and it takes ages to convert. 2 Days and only 170000000 from 700000000 inodes are converted by the tool.

      Did anyone have the same experince while converting from ext3 to btrfs

      Im using 3.16 bpo Kernel and the latst BTRFS Tools V3.18 from git.
    • Ext4 to btrfs in my rootfs. 8gb in like 30 minutes if I recall. I use btrfs in my data, but I've never though about converting it. I've brought one of the drives down from the raid1 and formatted then rsync it. Convert it to raid1 btrfs and balance the array.
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