On 25/03/14 07:15, Slava Barinov wrote:
Hello,
I've been using a single drive btrfs for some time and when free space
became too low I've added an additional drive and rebalanced FS with
RAID0 data and RAID1 System and Metadata storage.
Now I have the following configuration:
# btrfs fi show /btr
Label: none uuid: f9d78880-10a7-439b-8ebd-14d815edbc19
Total devices 2 FS bytes used 415.45GiB
devid 1 size 931.51GiB used 222.03GiB path /dev/sdc
devid 2 size 431.51GiB used 222.03GiB path /dev/sdb
# btrfs fi df /btr
Data, RAID0: total=424.00GiB, used=406.81GiB
System, RAID1: total=32.00MiB, used=40.00KiB
Metadata, RAID1: total=10.00GiB, used=8.64GiB
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sdb 1.4T 424G 437G 50% /btr
I suppose I should trust to btrfs fi df, not df utility.
So the main question is if such "asymmetric" RAID0 configuration
possible at all and why does btrfs ignore ~500 GB of free space on
/dev/sdc drive?
Also it's interesting what will happen when I add 20 GB more data to
my FS. Should I be prepared to usual btrfs low-space problems?
Best regards,
Slava Barinov.
The "raid0" will always distribute data to each disk relatively equally.
There are exceptions of course. The way to have it better utilise the
diskspace is to use either "single" (which won't get the same
performance as raid0) or to add a third disk.
In any raided configuration, the largest disk won't be fully utilised
unless the other disks add up to be equal to or more than that largest disk.
Play around with Hugo's disk usage calculator to get a better idea of
what the different configurations will do: http://carfax.org.uk/btrfs-usage/
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Brendan Hide
http://swiftspirit.co.za/
http://www.webafrica.co.za/?AFF1E97
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