Howdy,
I recently setup a new BTRFS filesystem based on BTRFS version 3.12 on
Linux kernel 3.13-1 running Debian Jessie.
The BTRFS volume spans 3x 4TB disks, two of which are using the entire
raw block device, and one of them is using a partition (OS disks). The
setup is like so:
root@gra-dfs:/data/tmp# btrfs filesystem show
Label: none uuid: 63d51c9b-f851-404f-b0f2-bf84d07df163
Total devices 3 FS bytes used 3.03TiB
devid 1 size 3.61TiB used 1.01TiB path /dev/sda3
devid 2 size 3.64TiB used 1.04TiB path /dev/sdb
devid 3 size 3.64TiB used 1.04TiB path /dev/sdc
Btrfs v3.12
root@gra-dfs:/data/tmp# btrfs filesystem df /data
Data, single: total=3.07TiB, used=3.03TiB
System, RAID1: total=8.00MiB, used=352.00KiB
System, single: total=4.00MiB, used=0.00
Metadata, RAID1: total=5.00GiB, used=3.60GiB
Metadata, single: total=8.00MiB, used=0.00
root@gra-dfs:/data/tmp#
root@gra-dfs:/home# mount | grep /data
/dev/sda3 on /data type btrfs (rw,noatime,space_cache)
root@gra-dfs:/home#
The setup is supposed to be "RAID-0 like" but with different size drives
within the volume, I created the BTRFS filesystem using the following
command based on the WiKi[1]
mkfs.btrfs -d single /dev/sda3 /dev/sdb /dev/sdc -f
Once setup, I transferred roughly 3.1TB of data and noticed the write
speed was limited to 200MB/s. This is the same write speed that I would
see across a single device. I used dd with oflag=direct and a block size
of 1M and a count of 1024 from /dev/zero. Both showed the same speeds.
So my question is, should I have setup the BTRFS filesystem with -d
raid0? Would this have worked with multiple devices with different sizes?
[1]:
https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices
--
Adam Brenner <[email protected]>
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