>> And I suspect that XFS swidth/sunit settings will still work >> with RAID-10 parameters even over plain LVM logical volume on >> top of that RAID 10, while the settings would be more tricky >> when used with interleaved LVM logical volume on top of >> several RAID-1 pairs (LVM interleaving uses LE/PE-sized >> stripes, IIRC). Stripe alignment is only relevant for parity RAID types, as it is meant to minimize read-modify-write. There is no RMW problem with RAID0, RAID1 or combinations. But there is a case for 'sunit'/'swidth' with single flash based SSDs as they do have a RMW-like issue with erase blocks. In other cases whether they are of benefit is rather questionable. > One would use a linear concatenation and drive parallelism > with XFS allocation groups, i.e. for a 24 drive chassis you'd > setup an mdraid or lvm linear array of 12 RAID1 pairs and > format with something like: $ mkfs.xfs -d agcount=24 [device] > As long as one's workload writes files relatively evenly > across 24 or more directories, one receives fantastic > concurrency/parallelism, in this case 24 concurrent > transactions, 2 to each mirror pair. That to me sounds a bit too fragile ; RAID0 is almost always preferable to "concat", even with AG multiplication, and I would be avoiding LVM more than avoiding MD. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
