Re: Max IO size

Connor McDonald <connor_mcdonald_at_yahoo.com> wrote in message news:<3B966E0C.3BA_at_yahoo.com>...
> I've got a sun (solaris 2.8) box with with datafiles under vxfs. After
> setting
>
> - maxphys to 512k
> - vxiomax to 512k
> - db block size to 8k
> - multiblock read count to 64
>
> I had presumed that I could get a ceiling of half a meg per read on
> (say) a full table scan, but a level 8 10046 trace yields a ceiling of
> 256k (ie p3 in the waits is 32 not 64)
>
> I'll be repeating the test under a raw partition tomorrow but comments
> anyone ? As a related question, anyone know what Oracle's SSTIOMAX is
> under the various versions (say from 7.3)
>
> Cheers

I have recently performed similar test. I believe your gating factor is at your VxFS's cache which by default is 256K.

If you use raw or Veritas' direct IO, you should be able to get 1024K - assuming you up multi_read_count to 128 and maxphys to 1024000.

I tried this on Solaris 2.7 and my P3 maxed at 128 ( 8K block ). However, I am unable to make it go higher regardless what I change. And if I mount VxFS with default, then the highest is only 256K.

My maxphys is set way above 1024000 - although I believe the highest it can go is 1 MB.

-Bass Chorng Received on Thu Sep 06 2001 - 14:39:08 CDT