ATA 4K sector issues

[Dag-Erling Smørgrav]

Thiago Damas <tdamas at gmail.com> writes:
> I tested now with 1Mb (2048 blocks) at the begining of disk, and same
> behaviour: slow write speed and high disk latency.

It just occurred to me - if I'm not mistaken, when the disk block size
is larger than either DFLTPHYS (64 kB), the kernel will do a
read-modify-write no matter how much data you write.  You should make
sure the filesystem never sees a block size larger than that (e.g. with
a four-disk stripe or a five-disk raid5, the individual disks' block
size should not exceed DFLTPHYS / 4, because the array's block size will
be 4 x the LCM of the individual disks' block sizes)

DES
-- 
Dag-Erling Smørgrav - des at des.no