On Fri, Jul 26, 2013 at 09:05:03AM +0200, Axelle wrote: > Hi btrfs folks, > > I'm afraid I have a newbie question... but I can't sort it out? It's > just about adding a disk to a btrfs volume and not getting the correct > amount of GB in the end... > > I have a btrfs volume which already consists of two different devices > and which is mounted on /samples. Its total size is 194G. > > $ df -h > Filesystem Size Used Avail Use% Mounted on ... /dev/sdc1 194G 165G 20G > 90% /samples > > Now, I would like to add another 500G to that volume, from another device. I did > > $ sudo mkfs.btrfs -m raid0 -d raid0 /dev/sdb > $ sudo btrfs device add /dev/sdb /samples > My filesystem now correctly reports: > > $ sudo btrfs filesystem show > Label: none uuid: 545e95c6-d347-4a8c-8a49-38b9f9cb9add > Total devices 3 FS bytes used 161.98GB > devid 3 size 465.76GB used 0.00 path /dev/sdb > devid 2 size 93.13GB used 84.51GB path /dev/sdc1 > devid 1 size 100.61GB used 84.53GB path /dev/sdc6 > But I miss some space when I do: RAID-0 requires at least two devices. If you balance this configuration, you'll use up the first 93.13 GiB of each device striping across all three devices, for a total of 3*93.13 = 279.39 GiB. Then /dev/sdc1 becomes full, leaving you with two devices which have 7.48 GiB and 372.63 GiB respectively. After another 7.48 GiB on each device (for a total of 2*7.48 = 14.96 GiB), you have filled /dev/sdc1, leaving only /dev/sdb to work with. Since there's only one device, it can't be used by RAID-0. If you want to use the full space available, you should rebalance to single usage, which stops the RAID-0 striping, and allocates linearly: # btrfs balance start -dconvert=single,soft /samples Hugo. > $ df -h > Filesystem Size Used Avail Use% Mounted on > ... > /dev/sdc1 660G 165G 43G 80% /samples > I added 500G! Why haven't I got more available?? > > To debug, I ran this command: > > $ sudo btrfs filesystem df /samples > Data, RAID0: total=162.00GB, used=159.79GB > Data: total=8.00MB, used=7.48MB > System, RAID1: total=8.00MB, used=24.00KB > System: total=4.00MB, used=0.00 > Metadata, RAID1: total=3.50GB, used=2.19GB > Metadata: total=8.00MB, used=0.00 > My data is in RAID0, that's ok. So where have my 500G gone, and how > can I fix this? > > Thanks > -- > 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 -- === 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 --- Sometimes, when I'm alone, I Google myself. ---
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