Slow performance

Ashley M. Kirchner ashley at pcraft.com
Mon Apr 30 17:58:07 UTC 2007


    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:

ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata1.00: ATA-7, max UDMA/133, 312581808 sectors: LBA48 NCQ (depth 0/32)
ata1.00: configured for UDMA/133
scsi1 : ahci
ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata2.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
ata2.00: configured for UDMA/133
scsi2 : ahci
ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata3.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
ata3.00: configured for UDMA/133
scsi3 : ahci
ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata4.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
ata4.00: configured for UDMA/133
scsi4 : ahci
ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata5.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
ata5.00: configured for UDMA/133
scsi5 : ahci


    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...

-- 
W | It's not a bug - it's an undocumented feature.
  +--------------------------------------------------------------------
  Ashley M. Kirchner <mailto:ashley at pcraft.com>   .   303.442.6410 x130
  IT Director / SysAdmin / Websmith             .     800.441.3873 x130
  Photo Craft Imaging                       .     3550 Arapahoe Ave. #6
  http://www.pcraft.com ..... .  .    .       Boulder, CO 80303, U.S.A. 





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