Slow disk I/O - was Re: Seeking Help

Sarunas Burdulis sarunas at math.dartmouth.edu
Thu Jan 24 14:04:34 UTC 2013


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On 01/24/2013 01:23 AM, geoff at thebakershome.net wrote:
> I should also point out that I get good speeds from hdparm on 12.10, just
> certain tasks are slow. ie. apt-get update "Reading package lists",
> transferring many files between drives (ie pictures), or compiling (cpu
> does not work for long periods of time while files are accessed).

Your hdparm -t results indicate good *disk device* access speeds. The
problem might then be with filesystem parameters, filesystem to disk
sector alignment, IO scheduler ("elevator").

You can run 'parted /dev/sda' and check alignment with align-check (type
help within parted).

For test purposes you can change "elevator" temporarily by appending
kernel boot parameter from GRUB. At GRUB screen press "e" and append,
for example, elevator=noop to the kernel line. Check
/sys/block/sda/queue/scheduler for the currently effective elevator (the
one in square brackets). "noop", "deadline" and "cfq" might be your
available choices.

- -- 
Sarunas Burdulis
http://math.dartmouth.edu/~sarunas
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