Those are buffered and not from the disk
use '-t'
On Wed, 14 Jun 2000, bug1 wrote:
> Ive been trying to overcome performance problems with software raid0,
> currently under 2.[34] a single drive has better read performance than a
> 4-way ide raid0 (striping), write performance seems to be limited to
> about 30MB/s, for me ide raid just doesnt scale well at all. Ive
> mentioned this on linux-raid mailing list and Ingo says that scsi scales
> well acording to his tests. Others on the list also noted poor ide
> performance.
>
> So... i think ide could have some performance limitations that are only
> noticable when using multiple disks.
>
> I modified hdparm to use 1280MB for Timing buffer-cache-reads to do the
> benchmark.
>
> I do hdparm -T /dev/hde i get 86MB/s then i do hdparm -T /dev/hdi i get
> 86MB/s
>
> If i do them both at the same time i get 43MB/s for each.
>
> The drives are udma66 each on there own promise udma66 pci card,
> detected and used by the kernel as udma66.
>
> Shouldnt the performance of these drives be independent of each other,
> why would one drive slow the other down ?
>
> I run it on a dual 433 celeron with 128MB ram, when i run only one
> instance of hdparm it uses 50% of cpu resources, when i run both
> concurrently combined they use 100% (aprox). So i assume hdparm isnt
> multi-thrreaded, given this i dont think cpu resource should be causing
> the bottleneck.
>
> Could this be a software (kernel) limitation rather than hardware ?
>
>
> Thanks
>
> Glenn
>
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>
Andre Hedrick
The Linux ATA/IDE guy
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