[CentOS] Slow performance

[Matt Martz]

On Mon, April 30, 2007 1:58 pm, Ashley M. Kirchner wrote:
>
>     Hi folks.
>
>     I'm posting this to both the Fedora as well as the CentOS lists in
> hopes that somewhere, someone can help me figure out what's going on.  I
> have a dual Xeon 3GHz server that's performing rather slow when it comes
> to disk activities.
>
>     The machine is configured with a single 160 GiB OS drive (with
> CentOS 5.0) and 4x500 GiB drives setup in a RAID-5 configuration.  All
> drives are setup for 3.0 GiB SATA link, and the motherboard also
> supports that.  Looking in dmesg when the system comes up, I see that
> reflected as well:
>
>     Now, I don't know what performance numbers *should* be, but on a 1.8
> GiB copy on the RAID (cp from one location to another on the RAID), it
> gets done in just under 50 seconds.  If I try to delete the folder
> afterwards (rm -rf FOLDER) it takes a few seconds to do so, however if I
> delete the CONTENTS of the folder, it does so within a fraction of a
> second (but then 'sync' takes a few seconds to catch up.)
>
>     That same folder that I'm copying contains 452 jpeg files in it,
> ranging from 2.5 to 6.2 MiB.  Doing some image processing on them is
> where it takes a long time.  At the moment I'm doing a simple thumbnail
> creation with the ImageMagick suite (convert FILE -thumbnail "200x200>'
> `basename FILE .jpg`.th.jpg) and it takes upwards of 8 minutes to
> complete.  The whole time it's running, 'top' reports the server load as
> follows: load average: 1.06, 1.00, 0.81  And the CPU usage is around 9%.
>
>     Interestingly, if I run the same command and have it create .png
> instead, it takes longer, but I won't go there just yet.  My question
> is, is this the expected performance on something like this, or should I
> be able to get better results?  Is there something I should or could do
> to speed up disk based processes?
>
>     Or is this something where it's more memory intensive and I need to
> look at adding more (right now it has 2 GiB of memory.)
>
>
>     This problem is causing one of our web sites to time out because
> it's trying to process hundreds of image files and generate thumbnails,
> and it's taking forever to do that.  So I'm starting at the bottom of
> the pile here, hardware.  If it turns out the hardware is fine, and
> there's nothing else that can be done to speed it up, then I'll move
> forward to other possible culprits, such as the routines within the site
> scripts themselves...

Try running "hdparm -Tt /dev/sda"  replace /dev/sda with the device name
for your hard disks.  After running that post back here with the results.

You can also install sysstat and use the sar command to see if your system
is indeed spening a lot of time waiting on disk reads and writes.

-- 
Matt Martz
CentOS Mirror Admin
mdmartz at gflug.net