On Sat, Mar 17, 2012 at 01:36:04PM +0000, Alex wrote: > > 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. > > > > > Isn't this going to be a problem for anyone restoring from a backup? Lots > > > of > > > data heading to btrfs without a pause. > > > > Again, not the issue here. > > Thank you HH for the explanation. > > What's the 'solution' though to Hugo's situation? > By 'solution' I mean the highest-utility way of dealing with unequal devices > problem in a two or more -up setting.
Use mkfs.btrfs -d single, as I said in another part of this thread. We have a bit of a problem right now with adding a second device to an existing FS with -d single, where the FS "upgrades" the single to RAID-0. However, there's patches from Ilya that stop that behaviour, and the restriper can be used to switch back to single after the "upgrade". > (I understand that we're violating the expectations of RAID0 and > have read the > http://btrfs.ipv5.de/index.php?title=FAQ#How_much_space_do_I_get_with_unequal_devices_in_RAID-1_mode.3F > about RAID1.) I'm working on a comprehensive explanation of the limits on btrfs's space usage, and a little JavaScript tool to help plan/explain disk usage. > Disks are (were) getting cheaper per MB faster than I could run out > of space! So I have increasing size array of drives - apparently the > similar situation as Hugo (I have three btrfs-ready drives). I don't have this problem personally. I just know something about the way btrfs allocates chunks. I think you meant Helmut has the problem. :) > I'm struggling how to mkfs.btrfs with this new knowledge whilst resolving it > with the btrfs storage pool concept. > > I stress there is a difficulty with my understanding not btrfs. 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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