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I have a MySQL Server that should be performing better than it seems to be. We're running ubuntu on a Amazon Cluster Compute (cc1.4xlarge)

Linux ip-10-0-1-60 3.2.0-25-virtual #40-Ubuntu SMP Wed May 23 22:20:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

Distributor ID: Ubuntu
Description:    Ubuntu 12.04 LTS
Release:    12.04
Codename:   precise

I have several output files from sar that i'm not really sure how to interpret. For example, I ran:

# Individual block device I/O activities
sar -d 1 180 > logs/block_device_io.log &

which gave me what looks like really high utilisation of my disk (turns out this block device maps to

/dev/xvdh on /var/lib/mysql type ext4 (rw,_netdev)

The output from my log:

10:48:59 PM       DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await       svctm     %util
10:49:00 PM dev202-16      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
10:49:00 PM dev202-32      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
10:49:00 PM    dev8-0      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
10:49:00 PM dev202-112   1008.00  31040.00   1416.00     32.20      1.02      1.01      0.89     90.00
10:49:00 PM dev202-80      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

Am I wrong in thinking this is a problem? I have it above 90% almost the entire time we're seeing slowness. Or does this just mean MySQL is doing what it's supposed to do?

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1 Answer 1

Am I wrong in thinking this is a problem? I have it above 90% almost the entire time we're seeing slowness.

Not wrong, that's definitely your problem. Disk I/O is your performance bottleneck, and while I don't think you've given us enough information to tell you how to fix it, if you want to improve performance, you need to either reduce load on your instance's disks, or increase the amount of disk I/O at your instance's disposal. (Honestly, I have no idea how you'd do that with an Amazon EC2 VM, though.)

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