hdparm shows poor performance on cached reads for PATA drive

[John Summerfield]

Konstantin Svist wrote:
> Konstantin Svist wrote:
>> I have an older laptop (HP ze4400 series) with a PATA hard drive.
>> When I check hdparm -T /dev/sda in Fedora 7 or 8, it shows me 
>> performance of ~180MB/sec
>>
>> When I use a boot CD (gparted/clonezilla) to check the speed (by the 
>> way, it uses the old style /dev/hdc, instead) - it tells me the 
>> performance is upward of 400MB/sec
>>
>> The buffered speed seems about the same in either case at ~30MB/sec. 
>> (I've tried enabling/disabling various settings via hdparm, while in 
>> boot CD mode)
>>
>> Why is this happening and is there a way to fix it (without reverting 
>> to /dev/hdc)?
> 
> 
> *bump* since I got no replies from last time
> Just ran another test: in F8, I get 123MB/s on cached reads, 28.55MB on 
> buffered reads. When booted into Knoppix 5.1.0, cached reads say 
> 210MB/s, and buffered reads fluctuate between 15MB/s and 20MB/s.

For general performance, cached performance is pretty irrelevant, you're 
still constrained to the bus speed at best, and the general ability of 
the hardware (ATA motherboard electronics included) in general.

I don't have the foggiest idea of what an HP ze4400 is; depending on its 
age your speed of 28.55MB is pretty good.





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Cheers
John

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