On Thu, 15 May 2014 09:31:42 Duncan wrote: > > Does the BTRFS RAID functionality do such staggered stripes? If not > > could it be added? > > AFAIK nothing like that yet, but it's reasonably likely to be implemented > later. N-way-mirroring is roadmapped for next up after raid56 > completion, however.
It's RAID-5/6 when we really need such staggering. It's a reasonably common configuration choice to use two different brands of disk for a RAID-1 array. As the correlation between parts of the disks with errors only applied to disks of the same make and model (and this is expected due to firmware/manufacturing issues) the people who care about such things on RAID-1 have probably already dealt with the issue. > You do mention the partition alternative, but not as I'd do it for such a > case. Instead of doing a different sized buffer partition (or using the > mkfs.btrfs option to start at some offset into the device) on each > device, I'd simply do multiple partitions and reorder them on each > device. If there are multiple partitions on a device then that will probably make performance suck. Also does BTRFS even allow special treatment of them or will it put two copies from a RAID-10 on the same disk? > Tho N-way-mirroring would sure help here too, since if a given > area around the same address is assumed to be weak on each device, I'd > sure like greater than the current 2-way-mirroring, even if if I had a > different filesystem/partition at that spot on each one, since with only > two-way-mirroring if one copy is assumed to be weak, guess what, you're > down to only one reasonably reliable copy now, and that's not a good spot > to be in if that one copy happens to be hit by a cosmic ray or otherwise > fail checksum, without another reliable copy to fix it since that other > copy is in the weak area already. > > Another alternative would be using something like mdraid's raid10 "far" > layout, with btrfs on top of that... In the "copies= option" thread Brendan Hide stated that this sort of thing is planned. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/ -- 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
