Posts Tagged ‘Checking and identifying server bottlenecks caused by hard drive DISK READ / DISK WRITE operations with iotop on Linux’

Checking and identifying server bottlenecks caused by hard drive DISK READ / DISK WRITE operations with iotop on Linux

Thursday, November 25th, 2010

As a server system administrator. Every now and then I have an overloading servers, where it is crucial to find the exact reason
for the server overloads / crashes.

In many occasions the top or htop are not enough for me to quickly get a server overload caused by a hard drive i/o operations.

When I got this kind of unusual problems caused by hard drives overheats, the system load avarage numbers increase tremendously. Still I had that cases in which the top shows only a couple of percents of server load and it seems initially like the problem is a kind of mystery.

At that cases I usually check the Hard Disk Drive (HDD) disk I/O operations to determine if, the file read and writes of the server are not exceeding the maximum amount of symultaneous read and writes a hard drive can support, or some kind of hardware problem is not causing a hard drive temperature overheats.

Of course the server hang ups caused by hard disk read or writes slowliness is not news but still it’s something that some administrators does fail to think about or even check and therefore often server access problems appear again and again for quite some time until the problem is identified and resolved.

Thus I wrote this small article to mention about the importance of the Linux System administrator to always have the iostat or sysstat utilities at hand and regularly use them to check the hard drive disk and writes to be sure server overloads doesn’t root at the hard drive read and write opeartions.

This is an absolutely necessary practice especially for busy servers.

My personal experience on the disk caused server slowliness and hangs are that this kind of problems with hard drive overheats more often occurs on servers running either an old hard ATA hard drives, or on Linux machines running Webserver or FTP, Samba etc. in which rapid file transfers from a huge number of clients is being requested or processed.

In that kind of shitty situations, installing and using the iotop will show you statistics about your hard drives Total DISK READ and DISK WRITES and will thus give you a hint if there is a server bottleneck caused by the harddrive.

The iostat is available for Debian package and installing it comes to;

debian:~# apt-get install iotop

Hope this article helps to some lame admin like me out there 🙂