Adaptect raid performance with FreeBSD

Karl Pielorz kpielorz at
Wed Jan 14 05:42:43 PST 2004

--On 14 January 2004 15:27 +0200 Ari Suutari <ari at> wrote:

> Hi,
> On Wednesday 14 January 2004 15:20, Karl Pielorz wrote:
>> > So, I get only about 25MB/s. Shouldn't I be getting something
>> > like 70 MB/s, or even more since there are two disks that
>> > can server read requests ?
>> Hmmm, what happens if you run two of those at once?
> 	Running 5 dd's at once gives in iostat:
> [snip]
> 	The peak seems to be 39 Mb/s.

Was that the peak 'each' - or combined? - i.e. what was the combined 
throughput for 2 dd's running?

>> PCI latency..
>> But, I can't remember seeing adjusting it making any real-world
>> difference - what happens if you max it out (e.g. 128, or 256)?
> 	I'll have to try this. However, I also doubt that it is not going
> 	to change anything.

Wouldn't be the first time :)

Give two dd's a run at the same, with 64k blocksizes and see what you get 
for each one...

We have a machine at the office with the same controller in it, and some 
IBM 36Gb 10K drives, but unfortunately it's not in any fit state to dd 
anything at the moment, else I'd give it a while :)


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