John Summerfield wrote:
Konstantin Svist wrote:
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).
Latency a problem on a laptop?
One of the tradeoffs one accepts in choosing a laptop is that it's
performance is going to be less than on less portable systems.
For starters, disks mostly spin at 5400 rpm instead of the usual 7200
on desktops and 10,000-15,000 on other systems.
Latency might be important in systems doing lots of short reads; then
seek time matters too. When loading multimegabyte programs and data
files into RAM so they can be paged out, forget it.
In general, I agree - but, again, this is not a 10-20% decrease, it's
almost 50%.
Plus, while investigating this, I've noticed that CPU performance
suffers heavily, as well (~50%).
Not only that, but hdparm says the cached reads are at ~175MB/s when I
drop into runlevel 1.
There's definitely something there that makes it so slow (I'm guessing,
a daemon) - and it doesn't affect my newer laptop.
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