On Thu, May 10, 2012 at 09:43:58PM +0200, Hubert Kario wrote: > On Thursday 10 of May 2012 12:40:49 Martin Steigerwald wrote: > > Am Mittwoch, 9. Mai 2012 schrieb Kaspar Schleiser: > > > Hi, > > > > > > On 05/08/2012 10:56 PM, Roman Mamedov wrote: > > > > Regarding btrfs, AFAIK even "btrfs -d single" suggested above works > > > > not "per file", but per allocation extent, so in case of one disk > > > > failure you will lose random *parts* (extents) of random files, > > > > which in effect could mean no file in your whole file system will > > > > remain undamaged. > > > > > > Maybe we should evaluate the possiblility of such a "one file gets on > > > one disk" feature. > > > > > > Helmut Hullen has the use case: Many disks, totally non-critical but > > > nice-to-have data. If one disk dies, some *files* should lost, not some > > > *random parts of all files*. > > > > > > This could be accomplished by some userspace-tool that moves stuff > > > around, combined with "file pinning"-support, that lets the user make > > > sure a specific file is on a specific disk. > > > > Yeah, basically I think thats the whole point Helmut is trying to make. > > > > I am not sure whether that should be in userspace. It could be just an > > allocation mode like "raid0" or "single". Such as "single" as in one file > > is really on one disk and thats it. > > I was thinking that "linear" would be good name for old style allocator. Please do distinguish between the replication level (e.g. "single", "RAID-1") and the allocator algorithm. These are distinct. Also, note that both of those work on the scale of chunks/block groups. There is a further consideration, which is the allocation of file data to block groups, which is a whole different thing again (and not something I know a great deal about), but which will also affect the desired outcome quite a lot. 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 --- Anyone who claims their cryptographic protocol is secure is --- either a genius or a fool. Given the genius/fool ratio for our species, the odds aren't good.
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