On 31 Aug 1999, Marc SCHAEFER wrote:
> Now, I just changed to have the 4 disks on the QLOGIC 1080 (U2/LVD),
> then 4 (2 each for each aic7xxx)
>
> -------Sequential Output-------- ---Sequential Input-- --Random--
> -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
> Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
> 2000 19712 97.6 85378 85.8 30903 73.0 26272 97.1 83648 92.1 323.2 3.8
>
> And with just the 4 disks on the QLOGIC:
>
> -------Sequential Output-------- ---Sequential Input-- --Random--
> -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
> Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
> 2000 19662 97.4 63567 64.3 21655 50.0 26064 96.0 68886 69.6 225.2 2.4
> For me, this means that we are saturating. [...]
i think you are hitting hardware limits. First, getting 85.3 MB/sec out of
your RAID0 array isnt all that bad :) But CPU load seems to be pretty
high, that could already be a limit. Also, DMA load is probably very high
(and coming from several devices) as well. It would be interesting to
check out the very same benchmarks with an identical but higher-clocked
CPU, to see how much the saturation point depends on CPU speed. (this
might not be possible with your system i guess)
-- mingo
