Hi,
On Thu, 29 Jul 1999 09:38:20 -0700, Carlos Hwa <[EMAIL PROTECTED]>
said:
> I have a 2 disk raid0 with 32k chunk size using raidtools 0.90 beta10
> right now, and have applied stephen tweedie's raw i/o patch. the raw io
> patch works fine with a single disk but if i try to use raw io on
> /dev/md0 for some reason transfer sizes are only 512bytes according to
> the scsi analyzer, no matter what i specify (i am using lmdd from
> lmbench to test, lmdd if=/dev/zero of=/dev/raw1 bs=65536 count=2048,
> /dev/raw1 is the raw device for /dev/md0). Mr. tweedie says it should
> work correctly, so could this be a limitation with the linux raid
> software? Thanks.
I'm back from holiday, so...
Ingo, any thoughts on this? The raw IO code is basically just stringing
together temporary buffer_heads and then submitting them all, as a
single call, to ll_rw_block (up to a limit of 128 sectors per call).
The IOs are ordered, so attempt_merge() should be happy enough about
merging. The only thing I can think of which is somewhat unusual about
the IOs is that the device's blocksize is unconditionally set to 512
bytes beforehand: will that confuse md's block merging?
--Stephen
