bottleneck of disk - performance quesiton

How one can find the bottleneck of a disk in Linux OS?
linuxpersonAsked:
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Natty GregIn Theory (IT)Commented:
that's does not happen to my knowledge, maybe formatting when setting up the disk, or disk is failing, Linux as far as I know does not have bottleneck of disk.
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TobiasHolmCommented:
You could use iostat:
$ iostat 3

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Example to show disk usage every third second.

$ iostat 3
          disk0       cpu     load average
    KB/t tps  MB/s  us sy id   1m   5m   15m
   65.89   6  0.38   1  1 97  1.35 1.21 1.12
   12.85  29  0.36   1  1 98  1.33 1.20 1.12
   16.00   1  0.01   1  1 98  1.33 1.20 1.12

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First you might have to install the iostat tool. Example in Debian:
sudo apt-get install sysstat

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Another tool is to measure the read/write performance with dd:
$ dd if=/dev/zero of=/tmp/test.tmp bs=500K count=1024
$ dd if=/tmp/test.tmp of=/dev/null bs=500K count=1024
$ rm /tmp/test.tmp

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Example:
root@comp:~# dd if=/dev/zero of=/mnt/3TB/test.tmp bs=5000K count=1024
5242880000 byte (5,2 GB), 154,418 s, 34,0 MB/s
5242880000 byte (5,2 GB), 148,747 s, 35,2 MB/s (ext3, write)
5242880000 byte (5,2 GB), 126,012 s, 41,6 MB/s (ext3, read)
root@comp:~# dd if=/dev/zero of=/mnt/4TB/test.tmp bs=5000K count=1024
5242880000 byte (5,2 GB), 151,988 s, 34,5 MB/s
5242880000 byte (5,2 GB), 144,414 s, 36,3 MB/s (ext4, write)
5242880000 byte (5,2 GB), 113,318 s, 46,3 MB/s (ext4, read)

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/Tobias
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arnoldCommented:
Vmstat should be checked as well to make sure your system is not requiring more memory than you have.
What does the system do?
Identifying your partitions with iostat 5 5
Will point to where your reads and writes .......
That may shed light on an issue.

How your disks are setup, partitioned, arranged might ..........

And the types in use
Fdisk -l

Do you sue LVM, software raid, etc.
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linuxpersonAuthor Commented:
no I don't use software RAID
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arnoldCommented:
What is the setup of your system, Manufacturer, RAID controllers, number of drives, CPU, MEMORY, etc.?
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joolsCommented:
try "atop" or "htop", I use atop, better than top but you will have to find/install it for your distro, it shows loads of info, including processes/memory and cpu/disk in an easy to read screen and you can log over time.

sar is another tool, use sar -d (might also need to be installed for your distro).
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