Greetings,
until yesterday I was running a btrfs filesystem across two 2.0 TiB
disks in RAID1 mode for both metadata and data without any problems.
As space was getting short I wanted to extend the filesystem by two
additional drives lying around, which both are 1.0 TiB in size.
Knowing little about the btrfs RAID implementation I thought I had to
switch to RAID10 mode, which I was told is currently not possible (and
later found out that it is indeed).
Then I read this [1] mailing list post basically saying that, in the
special case of four disks, btrfs-raid1 behaves exactly like RAID10.
So I added the two new disks to my existing filesystem
$ btrfs device add /dev/sde1 /dev/sdf1 /mnt/archive
and as the capacity reported by 'btrfs filesystem df' did not increase,
I started a balancing run:
$ btrfs filesystem balance start /mnt/archive
Waiting for the balancing run to finish (which will take much longer
than I thought; still running) I found out that as of kernel 3.3
changing the RAID level (aka restriping) is now possible: [2].
I got two questions now:
1.) Is there really no difference between btrfs-raid1 and btrfs-raid10
in my case (2 x 2TiB, 2 x 1TiB disks)? Same degree of fault
tolerance?
2.) Summing up the capacities reported by 'btrfs filesystem df' I only
get ~2.25 TiB for my filesystem, is that a realistic net size for
3 TiB gross?
$ btrfs filesystem df /mnt/archive
Data, RAID1: total=2.10TB, used=1.68TB
Data: total=8.00MB, used=0.00
System, RAID1: total=40.00MB, used=324.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=112.50GB, used=3.21GB
Metadata: total=8.00MB, used=0.00
Thanks in advance for any advice!
Regards,
lynix
[1] http://www.spinics.net/lists/linux-btrfs/msg15867.html
[2] https://lkml.org/lkml/2012/1/17/381
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
