What is hdparm "readahead"?

net_keeper · Posted: Tue Aug 19, 2003 11:41 am Post subject: What is hdparm "readahead"?

Hy,

Before some time I have complaint that my gentoo is slower than my old mandrake.

Well,
It have been fix with hdparm.

Now I have reset to my old mandrake and I found a different in the hdparm output.

Mandrake hdparm output:

/dev/hda:
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 8 (on)
geometry = 4865/255/63, sectors = 78165360, start = 0

And in my gentoo:

/dev/hda:
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 12009/16/63, sectors = 78165360, start = 0

Is the different is affective? Which is faster?

pilla · Posted: Tue Aug 19, 2003 11:55 am Post subject:

Have you read "man hdparm" ? The meaning of the read-ahead flag is described there.

You need to know what you want to maximize in your system (throughput x response) and run some benchmarking before you decide which one is better for you.
_________________
"I'm just very selective about the reality I choose to accept." -- Calvin

TobiWan · Posted: Tue Aug 19, 2003 7:06 pm Post subject: DMA off/on

Hi there,

while we're at it I thought I could just drop a question related to DMA and harddisks. While booting, I get a message in a nice ascii box, that devfs might be slowed down due to turned off dma. I can enable it using hdparm but the next time I boot, the message stays. Where can I set the dma permamently?

thanks in advance for a probably stupid question,
Tobias

hensan · l33t Joined: 26 Jun 2003 Posts: 868 Location: Sweden

Put your settings in /etc/conf.d/hdparm

Then do: rc-update add hdparm default

TobiWan · Posted: Tue Aug 19, 2003 7:25 pm Post subject: many thanks

many thanks, that does the trick!

this should go into http://www.gentoo.org/doc/en/gentoo-x86-install.xml ;-)

cheers,
Tobias