virtual grind thoughts from the virtual world

10Sep/140

Dell Compellent 6.4 Write Latency

Recently, I started seeing abnormal write latency across a number of pods in our environment. After spending a few hours looking at best practices and firmware on the compute and storage side, I decided to look at the switching layer. As expected, things like IO, buffers, buffer credits, etc. all looked fine.

Thinking it may be a cosmetic issue in Dell's Enterprise Manager, I engaged Compellent Support to have a look. After a week or so of analysis, I finally reached a senior engineer, who on a whim, asked me to test disabling SNMP at the controller level. In an instant, the abnormal write latency disappeared. What is alarming is that this was not just cosmetic, but actually felt all the way down to the host level.

I will say that I do not see this behavior in 6.3 but the change made a huge difference in 6.4.4.2 and 6.4.5.4. You can disable SNMP in Storage Center Manager by navigating to Storage Management -> System -> Access -> Configure SNMP Server, then click on "Stop Agent". If SNMP is not running, the link will say "Start Agent".

If you are running any FluidOS version 6.4.1 to 6.4.10, you may want to upgrade or disable SNMP and feel the difference!

Please note the change was made around 11AM, screenshots attached (click to view):

Controller View

Host View

Virtual Machine View

9Oct/120

Restarting DRAC Interface

I recently ran in to a few situations where the DRAC web interface was acting funny.

In one event, when I would log in to the DRAC web interface, despite having the correct username and password, the web interface would just bring me back to the main login page. The second scenario would let me in the main DRAC admin page, but I could not launch a remote console.

Anyway, there is a very simple fix. Simply ssh into your DRAC ip address with the same username and password you use to access the web interface. Once you ssh in, you will be at the main DRAC admin prompt. To reset DRAC and NOT lose any settings, simply enter the command:

racadm racreset soft

20Jan/110

Dell Hooks Server Tools Into VMware vCenter

Awesome new plugin from Dell, great to see more hardware vendors plugging in to VCenter.

Check it out here.