On Fri, Mar 29, 2013 at 03:18:03PM +0100, Harald Glatt wrote: > Sorry I forgot to post that, > > -> btrfs fi show > Label: none uuid: 2feccf06-5af8-4d8a-ad8d-a090cf4ef69a > Total devices 2 FS bytes used 16.54GB > devid 1 size 40.90GB used 14.04GB path /dev/sda7 > devid 2 size 17.75GB used 14.03GB path /dev/sda6 > > The array is more of a for-fun and testing thing than a real world > example. I've simply combined two differently sized partitions on the > same disk together. > > So how much space is actually used now? > > On Fri, Mar 29, 2013 at 3:12 PM, Josef Bacik <jba...@fusionio.com> wrote: > > On Fri, Mar 29, 2013 at 07:58:40AM -0600, Harald Glatt wrote: > >> I've run a balance before taking these meassurements: > >> > >> -> df -h reports 59G total space, 18G used, 7G free. > >> -> btrfs fi df / reports the following: > >> Data, RAID0: total=16.00GB, used=15.58GB > >> System, RAID1: total=32.00MB, used=4.00KB > >> System: total=4.00MB, used=0.00 > >> Metadata, RAID1: total=6.00GB, used=974.36MB
OK, so you have 14.04+14.03 = 28.07 GiB allocated for immediate use on the disk. Of that 28.07 GiB, - 16.00 GiB is assigned for RAID-0, and 15.58 GiB of that is actually occupied by useful data. - 6.00*2 = 12.00 GiB is assigned for use by RAID-1 metadata, giving 6.00 GiB of usable metadata. 974.36 MiB of that contains actual metadata. - 68.00 MiB (2*32.00 + 4.00) is the remainder, assigned to the system chunks (actually the chunk tree), of which 4 KiB is actually useful data. Now, since you have RAID-0 data, the FS requires at least two devices to stripe across. So the best it can manage is to add a further 3.75 GiB of data chunks on each device (because /dev/sda6 has 3.75 GiB not allocated). 3.75 GiB on two deivces for RAID-0 is 2*3.75 = 7.5 GiB reported free by df. HTH, Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- Gentlemen! You can't fight here! This is the War Room! ---
signature.asc
Description: Digital signature
