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Trouble Shooting High Disk I/O Problems

Posted by Allura on 11 07 2018.

Disk I/O reports the duration of reading and writing operations required by a hard disk. The performance of your server, cPanel and WHM is affected by the speed at which your server is capable of reading and writing information to disk. If your system experiences high disk I/O wait time it will lead to an increased load on your server.

Symptoms of High Disk I/O

Problem Description
High server load The average load of the system is greater than 1.
Notifications from chkservd Notifications are sent when a service goes offline or that the system fails to restart a service.
Hosted websites are slow It may take more than a minute for hosted websites to load.
Emails are delivered late The Exim service’s performance slows down or it stops responding. Exim contains a huge amount of outbound mail list.
Email has a slow connection Slow performance by POP or IMAP services or they stop responding.
Slow Webmail interfaces The performance of Webmail interfaces slows down or they stop responding (example: Horde, Roundcube, or SquirrelMail).
WHM or cPanel interfaces work slow Adding databases, email accounts, or other items makes the WHM or cPanel interfaces perform slowly.

 

Determining the Disk I/O Wait on Your Server

The top command will help you to find the average wait time on your server. Your server’s average disk wait time is indicated by the %wa statistic. It can be found at the top of the output screen. Data processing on hard disk by the CPU cores is delayed if the I/O wait percentage is more than one divided by the number of your CPU cores. The sar command will provide you with details like the history of your server’s disk I/O wait.

How to Resolve a Problem with high Disk I/O

Problem Solution
Degraded RAID array Check whether the Raid array has a hardware malfunction. The hardware should be tested and verified.
Hard disk features having less RPM speed or an interface technology that is working slow Upgrade your server hard disk. You can also split the application load between different hard disks.
The hard disk has run out of bandwidth Upgrade your server hard disk. You can also split the application load between different hard disks.
Software processing speed is slow Upgrade your server hard disk. You can also split the application load between different hard disks.
Busy report by the Software RAID array; CPU is using slow parity calculation Look for a hardware malfunction in the Raid array. The hardware should be tested and verified.
Disabled write caching Write caching on the disk should be enabled.

 

 A Concluding Note

As evident, this interface provides a range of features which provides a list of key features, which would help cPanel Admins resolve Disk I/O problems.