Re: why raid5 not like this?

On Tuesday June 13, xshu2006@gmail.com wrote:

in linux raid4/5/6  ,one big bio will span several devices,and There
may be several bio's per stripe+device.if the bio arrived in bi_sector
with overlap,we must wait the former bio to be finished.
why not we split the bigger bio into small ones?we can attach the
smaller bio to the stripe+device (here we may can do some merge ).one
disk i/o we can finish many small bios.if all the small bios of the
request be finished ,we can return the request.

Overlapping bios are expected to be extremely uncommon, so any
optimisation is pointless.

Do you have reason to believe that overlapping bios are sufficiently
common that the current code is causing problems?

NeilBrown