Saturday, May 7, 2016

ESXi Queue Depth

The HBA LUN queue depth determines how many commands the HBA is willing to accept and process per LUN and target.

ESXi 5.x the ddefault value for ql2xmaxqdepth=64, if a single VM is issuing IO, the queue Depth setting is applicable.

When multiple VM's are simultaneously issuing IO's to the LUN, the ESX parameter Disk.SchedNumReqOutstanding (DSNRO) value becomes the leading parameter, and HBA Queue Depth is ignored.

Increading the Queue Depth value without changing the Disk.SchedNumReqOutstanding setting will only be beneficial when one VM is issuing commands. It is considered best paactice to use the same value for the Queue Depth and DSNRO.


Type esxtop and press d:disk adapter:

The value listed under AQLEN is the queue depth of the storage adapter. This is the maximum number of ESX VMKernel active commands that the adapter driver is configured to support.


Type esxtop and press u: disk device:  

DQLEN limits the commands per storage device.
The value listed under DQLEN is the queue depth of the storage device. This is the maximum number of ESX VMKernel active commands that the device is configured to support.

So basically I can multiply the LUN queue with the number of connected datastores to know how much active commands my host is allowed to issue down to the storage. This value will be limit by AQLEN to 2176 per vmhba.

What’s the Best Setting for Queue Depth?

VMware default settings are usually preferred. However, It is highly unlikely that all hosts perform at their maximum level at any one time. Changing the defaults can improve throughput, but most of the time it is just a shot in the dark. Although you are configuring your ESX hosts with the same values, not every load on the ESX server is the same.. Please do not change the default settings unless directed to by VMware in conjunction with the storage vendor. Changing these settings without analyzing the environment can be more harmful than useful.


Praylin S said...

It's great to come across a blog once in a while that's not the same outdated material. Really glad that I came across your post. Keep us updated.
VMware Training in Chennai
VMware Course in Chennai
Spark Training in Chennai
Spark Training Academy Chennai
C C++ Training in Chennai
C Training in Chennai
VMware Training in Velachery
VMware Training in Anna Nagar

Sadhana Rathore said...

I wanted to thank for sharing this article and I have bookmarked this page to check out new stuff.
Machine Learning course in Chennai
Machine Learning Training in Chennai
Data Science Course in Chennai
Data Science Training in Chennai
DevOps certification in Chennai
DevOps Training in Chennai
Machine Learning Training in Velachery
Machine Learning Training in Tambaram

Anonymous said...

Nice Post! I appreciate to you for this post. Really you are the best. VMware Certified Professional Exam Dumps

Realtek Consulting said...

It’s awesome that you want to share those tips with us. It is a very useful post Keep it up and thanks to the writer.

erp providers in chennai
erp implementation in chennai
erp software in chennai
UiPath Automation Chennai

Anonymous said...

Thanks for sharing such a great blog Keep posting.. 
VMware Training in Delhi
VMware Course in Delhi

monu said...

Thank you for excellent article.Great information for new guy like antimalware service executable

Azure VMware Solution by CloudSimple - AVS

CloudSimple provides native VMware Private Clouds as-a-Service from the Azure Public Cloud. Overview Microsoft Azure VMwa...