Adaptect raid performance with FreeBSD

[Phil Kernick]

A note from the dump(8) man page...

      Currently, physio(9) slices all requests into chunks of 64 KB.  There-
      fore, it is impossible to use a larger output block size, so dump will
      prevent this from happening.

Same thing likely happens with dd, so bigger than 64k doesn't ever help.


Phil.

Ari Suutari wrote:

> On Wednesday 14 January 2004 15:02, Raymond Wiker wrote:
> 
>>Ari Suutari writes:
>> > dd if=/dev/rda1s1a of=/dev/null bs=1m count=100
>> > 100+0 records in
>> > 100+0 records out
>> > 104857600 bytes transferred in 4.193832 secs (25002814 bytes/sec)
>> >
>> > 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 ?
>>
>>        Have you tried other block sizes? I think you may be able to
>>get better results by going to a lower block size (e.g, 64k instead of
>>1m). Some experimentation will show which block size(s) work best.
> 
> 
> 
> 	I tried with 32k, 64k, 256k and 512k. Speed is about the same
> 	with every block size. Block sizes less than 32k seem to give
> 	even worse performance.
> 
> 		Ari S.	
> 


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