Storage metrics
Before we start exploring disk performance metrics, I will walk you through three different screens for the disk metrics. The first storage metrics screen is called disk device view, where you can view LUN information; the second one is the disk VM screen where you can see the statistics per virtual machine basis; and the last one is the disk adapter screen where you can view the information of disk statistics per host bus adapter (HBA) basis.
Let's access esxtop to view the disk statistics in the LUN mode:
- Connect to a vSphere host using SSH and log in as root or an administrative user.
- In the command prompt, type
esxtopwithout any flags. - Press u to switch disk device screen. This screen displays detailed information about storage, including your LUN, available data stores, shares, and number of objects.
- Press f to go into Current Field Order screen.
- You need to enable some additional information for the Number of Objects and Shares fields. Press c and then press d to enable the preceding fields.
- Press the Esc key to return to the esxtop disk statistics screen.
- Press s and enter
2to set the refresh time to every 2 seconds. It will bring to you the following screen:
Figure 2.11
For your application workloads, I/O latency from 20 milliseconds to 25 milliseconds can result in performance degradation. Though this is not a hard and fast rule for I/O intensive applications these values can significantly differ. For example, one application can be very IO intensive while the other application may not be as such. As I have stated in the preceding table, GAVG is a total of two latencies: DAVG and KAVG. Ideally, KAVG should be as miming as possible: the best value to achieve is zero, and the threshold value can be considered as 2 milliseconds. In addition to this, GAVG and DAVG should not be increased more than 25 milliseconds, or your system will have some I/O performance issues and the problem will need to be investigated further. You can start investigating from the storage metrics and expand the investigation to your SAN, LUNs, and storage switches.
Tip
Downloading the example code
You can download the example code files from your account at http://www.packtpub.com for all the Packt Publishing books you have purchased. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.
Using vMA and resxtop
As part of vCli, rsxtop is a remote version of esxtop that comes up with the vMA appliance. Rsxtop can also be used in three operational modes: interactive, batch, and replay modes. Perform the following instructions to use resxtop from VMWare vMA appliance to examine the network matrices:
- Log in to vMA as vi‑admin.
- Add a server as a vMA target by running the following command:
vifp addserver crimv3esx002.linxsol.com --authpolicy fpauth - Now set it as the target server to perform operations:
vifptarget --set crimv3esx002.linxsol.com - Once the target is set, simply type the following command in the console:
resxtop. - This will take you to the esxtop interactive command, where you can follow the procedures described to interact with different vSphere host performance metrics.
- Once you are done, type the following command in the console to remove the target server from vMA:
vifpremove removeserver crimv3esx002.linxsol.com
Figure 2.12