On Sat, Mar 17, 2012 at 02:46:00PM +0100, Helmut Hullen wrote: > Hallo, Hugo, > > Du meintest am 17.03.12: > > [no space left on device ...] > > >>> Where is the problem, how can I use the full space? > > >> Effectively it's missing the trigger to rebalance when the 'primary' > >> device starts to get full, or just to randomly spread the data > >> between the devices. > > > No, a balance isn't going to help here. RAID-0 requires a minimum > > of 2 chunks in a block group. With two disks, you're only going to be > > able to fill the smallest one before you run out of space. > > Ok - it happens only with 2 disks/Partitions?
Not quite. With the current RAID-0 implementation, you will lose the difference between the largest disk and the second-largest. There's a proposal from November that may help with that, but I haven't had a chance to look at it yet to see what the implications are. > I've continued playing; added a 3rd partition/device and then balanced: > > > # btrfs device add /dev/sdd1 /mnt/btr > ## 73 + 146 + 146 GByte OK, so in this case the largest and second-largest devices are the same, so you will lose no space. [snip] > Looks as desired, the 3-disks-system contains more than 3 times the > smallest disk. > > Balancing hasn't redistributed the contents - no problem. > > By the way: you should name the prefixes in the NIST way for powers of > 2: KiB, MiB, GiB. Or change to decimal prefixes. I know. It's something I submitted patches for a long time ago, and they never got taken up. It's on my list of things to fix. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- UNIX: Spanish manufacturer of fire extinguishers. ---
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