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I have a CentOS server with 2 hard drives configured to use LVM over RAID1.

How do I benchmark my hard drive? As seen in this question, I have used the following commands:

# check read performance
sudo hdparm -Tt /dev/sda
# check write performance
dd if=/dev/zero of=/tmp/output bs=8k count=100k; rm -f /tmp/output

But I got roughly the same figures as I got on a single disk, before configuring the RAID array. Now I figured that I should be explicitly using the LVM drive instead of /dev/sda and /tmp/output. I must have done something wrong here, as the system stopped finding crucial system files such as yum. I failed to write down the exact commands I used and I had to reinstall the system at this point.

So, what commands should I use to check disk perfomance of LVM drive? And, most important, what kind of commands should I not use?

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/tmp is usually a ramdisk these days. Are you sure you are actually testing a filesystem stored on your disk? In any case look into iometer, or bonnie++ tools really meant for testing. –  Zoredache Mar 27 at 16:43
@Zoredache Can you tell me which numbers to look at? The output looks confusing. –  Nickolai Leschov Mar 27 at 17:01
Your write performance should be roughly the same as on a single disk on a RAID 1. You're still writing the same amount of data to each individual drive as you would be with a single disk. As for what you should use to benchmark, you should use whatever most closely mimics the intended usage if you can't run the actual load you intend to on it. –  yoonix Mar 27 at 17:36
@yoonix I would like to quickly probe for read performance increase. Yet I'm not familiar wit LVM and don't know which device should I probe instead of /dev/sda? –  Nickolai Leschov Mar 27 at 18:11
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