Hi Hugo, Thanks for your answer, but I'm afraid I still don't get it. >RAID-0 requires at least two devices. Well, I have three devices, so that's more than enough isn't it? Or do you mean I should be adding two devices at a time? > 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 why 93.13? I guess you meant 84.53 which is the size I am using on sdc1 and sdc6. ># btrfs balance start -dconvert=single,soft /samples Nice command but I wasn't thinking of stopping RAID0 striping. I was expecting my data to be stripped evenly on all 3 devices. Well - evenly - until the smallest one /dev/sdc1 is filled, then, it'll use only the last two, when /dev/sdc6 is filled, it will used /dev/sdb only. Is that possible/correct? But basically, what does not make sense to me is what df reports as available size. Look. Before, I had ~165G used on a total of 194G. I added a new disk of 465G. Now, df reports I have a total of 660G (that's right) with 165G used (that's correct too) but only 43G available! I was expecting to have ~495G available! Where are my 465G gone? $ df -h Filesystem Size Used Avail Use% Mounted on ... /dev/sdc1 660G 165G 43G 80% /samples Thanks Axelle. On Fri, Jul 26, 2013 at 9:45 AM, Hugo Mills <hugo@xxxxxxxxxxxxx> wrote: > 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. --- -- 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
