Re: Very poor IO performance (high CPU load), libata

From: Carsten Otto
Date: Sun Jul 16 2006 - 05:36:52 EST

Problem solved!

On Sat, Jul 15, 2006 at 07:45:57PM +0200, Carsten Otto wrote:
> In the problem case the IO wait never drops below 40% no matter how light
> the HDD load is. Logging in into the system via SSH then takes more than
> two minutes and other tasks are equally slow.

Okay, the wait percentage is no problem, but the speed is.
I had to use a second power supply for two of the four SATA disks,
because the main supply is not good enough and causes crashes and
reboots (see my other threads, I will answer there too).
In a test that checked each disk seperately I noticed that exactly those
disks connected to the second power supply perform very poor with write
accesses (65 MB/sec vs. 2 MB/sec). I replaced the second (bad) power
supply with a very good one and now all disks are working fine. My new
main power supply should arrive soon.

I still can't understand why disks work slower when provided with
"wrong" power... The disks are Maxtor MaXLine III 7V300F0.

> There might be a problem with my hardware (in a not yet determined
> device) causing this problem. But as long as I do not know what is wrong
> I still see the chance of a software error in the kernel.

Yeah, the kernel is okay :)

PS: Now a very annoying hunt for some error in my computer ends after
about three weeks. The system now is stable and fast and I am happy...

Bye and sorry for bugging you,
Carsten Otto
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