While in specific use cases it may be preferable to fill up one disk and then move on to the next, that does not get you the best performance, so I suspect you will be hard pressed to find any "real" filesystem that behaves in such a way. You may be able to do that with aufs, but if you you want to limit data loss in the event of a failure, you probably want to always write to the disk with the most free space which aufs can do.
On Mon, Mar 18, 2013 at 1:04 PM, Jan Beranek <jan233...@gmail.com> wrote: > Thank you for the test. > > I will do some tests also (later as now I do not have a space for it) > - when you disconnected one disc (or deleted a file) did you try btrfs > fi balance? I wonder if missing files simply "disappears" or not, > because in the fact they are present as metadata information only. if > not, then would be necessary to write a small script which will check > all the files and report missing/broken ones (or use aufs on top). > > When I use "-d single" option, then preffered way is fill the disc > completelly and then continue with another disc. And you are right, > there is no guarantee that some files wil not be spread over all three > (or more) disc. (as I understand it from docs). > > On Mon, Mar 18, 2013 at 9:03 PM, Jan Beranek <jan233...@gmail.com> wrote: >> Thank you for your test. >> >> I will do some tests also (later as now I do not have a space for it) - when >> you disconnected one disc (or deleted a file) did you try btrfs fi balance? >> I wonder if missing files simply "disappears" or not, because in the fact >> they are present as metadata information only. if not, then would be >> necessary to write a small script which will check all the files and report >> missing/broken ones (or use aufs on top). >> >> When I use "-d single" option, then preffered way is fill the disc >> completelly and then continue with another disc. And you are right, there is >> no guarantee that some files wil not be spread over all three (or more) >> disc. (as I understand it from docs). >> >> >> On Mon, Mar 18, 2013 at 8:24 PM, cwillu <cwi...@cwillu.com> wrote: >>> >>> On Mon, Mar 18, 2013 at 12:32 PM, Jan Beranek <jan233...@gmail.com> wrote: >>> > Hi all, >>> > I'm preparing a strorage pool for large data with quite low importance >>> > - there will be at least 3 hdd in "-d single" and "-m raid1" >>> > configuration. >>> > >>> > mkfs.btrfs -d single -m raid1 /dev/sda /dev/sdb /dec/sdc >>> > >>> > What happen if one hdd fails? Do I lost everything from all three >>> > discs or only data from one disc? (if from only one disc, then is it >>> > acceptable otherwise not...) >>> >>> I just finished doing some testing to check: It will work, kinda sorta. >>> >>> You'll be forced to mount read-only, and any reads of file extents >>> that existed on the missing disk will return an io error. As I >>> understand it, single doesn't force files to be on a single disk, >>> instead it _doesn't_ force them to be _several_ disks; the implication >>> being that a large file (say, a 4gb movie) may still end up with >>> pieces on each disk. >> >> >> >> >> -- >> S pozdravem >> >> Jan Beránek > > > > -- > S pozdravem > > Jan Beránek > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Michael Johnson - MJ -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
