FreeBSD 5.3b7and poor ata performance

[fandino]

Søren Schmidt wrote:
>>>
>>> please can you post how do you solved the problem?
>>
>>
>> atacontrol mode <channel> DMA4 DMA4
>> atacontrol mode <channel2> DMA4 DMA4
>>
>> The reason is that the motherboard only supports ATA100 on two out of 
>> four IDE channels and hence you need to force the two other channels 
>> to run at DMA66 
> 
> 
> How do you come to that conclusion ? There is no such limitation AFAIK.
> 
> However you can only get a total sum of 133MB/s divided by number of 
> disks (and minus some overhead on older system there is typically 
> 110MB/s effective bandwidth)..
> 
> The real explanation is much more likely that the timing specs are 
> marginal (overclocked ?) for the disks, which causes problems..


no, it is my home PC in which I work so it's important stability
(not overclocking) and disk redundancy (vinum, gmirror)

Also, there is an unresolvable question. Why two 52MB/s disks
in raid0 has a throughput of 40MB/s and for raid1 18MB/s??