On Wed, 15 Jul 2009, Andreas Dilger wrote: > I've been trying to get some steam behind a more common interface for > backing up and restoring file layout information, using virtual xattrs. > > This will allow tar/rsync/etc to back up the layout xattr and then > restore it (preferrably before the data is written) to the target, > so that any user-specified file layout is preserved. > > I'm thinking of using simple ASCII key=value pairs to store basic > layout information like chunk size, stripe count, mirror count, > RAID type, etc. Some of them may not be applicable/usable by all > filesystems, but having a handful of "well known" keys and values > for a common xattr name would at least be better than what we have > now (which is nothing). > > Something like (not necessarily a firm proposal yet): > > trusted.common_layout: > chunk_bytes=65536 > stripe_count=32 > mirror_count=3 > raid_type=1+0 > > Is this something you would be interested to pursue? I've also discussed > this with Panasas, and they had some interest in this as well. Any GPFS > developers watching? This sounds like a good idea to me. I think the main hurdle is going to be defining a generalized layout description that captures all the full space of layouts for each file systems, and also translates gracefully between them. IIRC Lustre, for instance, will stripe over $stripe_count objects, while Ceph (and Panasas?) will stripe up to some $max_object_size and then move on to a new set of objects. Or stagger chunk order in successive stripes, etc. The ioctl approach sucks, and I'd be happy to replace it out in favor of something more generic. sage -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
