Question Slow File I/O and Read/Write Speeds on VPS

[steveb]

Hi all,

We are experiencing slow 'file open', 'file close' and read/write speeds on our hosted VPS server in LAMP stack with CENTOS and PLESK.

When you run a test like..

-bash-4.1$ dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync

you get reasonable speeds (155 Mb/sec), but when you run a simple BASH script that reads the contents of a simple .txt file, we're seeing response times 10X slower than comparable servers (same script - one on VPS another in shared hosting). This seems to be one reason non-cached pages on our our Magento installation are significantly lagging.

Is there any chance this could be a PLESK related issue?

We assume not, but are just checking - in the off-chance anyone has seen this before.

Suggestions appreciated!

 

[IgorG]

I don't think that it is Plesk related issue. I don't know what sort of virtualization solution do you use, but in case of Virtuozzo there are many tools and settings can be applied for increasing i/o performance for patricular VPS. For example, to monitor I/O operations, you can use the vziotop utility. Also reads from disk are not only using disk resources, CPU is also involved into any I\O operations. Therefore the results may be affected by the CPU settings assigned to the VPS.
So, this issue should be investigated from hardware node side for your VPS.

 

[steveb]

Thanks for the quick reply Igor. Good to get the confirmation re. PLESK.

Wasn't aware of the utility nor CPU angle. Will look into it.

Cheers