disk i/o kills network [solved]

juhah · n00b Joined: 03 Oct 2004 Posts: 46

Heavy disk i/o forces network down to its knees. For example while extracting huge archive in file server and trying to copy something from that server via nfs is impossible.

* Any TCP/IP uploads from the machine are practically stalled.
* TCP/IP downlink (e.g. downloads and web browsing) is sticky.
* Network traffic forwarding slows notably.
* Seen on several architectures (x86 and amd64)
* Seen on several distributions (Gentoo and Fedora)
* Seen on IDE and SATA disks.
* Top reports that 80-99 % of cpu usage is i/o wait (quite natural)
* load is very high
* nice'ing has effect little to none

This is REALLY annoying. Could enabling of kernel preemption help?

inode77 · Posted: Sat Apr 02, 2005 4:21 pm Post subject:

Disable IRQ sharing for IDE controllers and recompile your kernel.
On a desktop preemption is considered usefull so I'd enable it.
Play with different schedulers.
Not sure if it helps but it's worth a try.

juhah · n00b Joined: 03 Oct 2004 Posts: 46

Thank you!

It was the scheduler. I don't know what is the default but elevator=cfq did the trick (kernel 2.6.11). The difference is remarkable!