Re: hdparm shows poor performance on cached reads for PATA drive

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John Summerfield wrote:
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.


I agree that cached performance doesn't matter all that much, normally. However, it's a pretty large drop in performance - and I'm trying to figure out why it happened. I wouldn't be worried about it if it were off 5-10% - but it's just about HALF of the old value. Also (and I'm not sure about this...) this might indicate some problem with latency (which *would* be pretty important, especially if it's this much).


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