Tech Notes

I was talking with an independent contractor a few days ago and she mentioned that more than a few customers justify buying storage management tools by using them to find unused disk space. It’s pretty common to find allocated but unused space that often amounts to tens or even hundreds of thousands of dollars’ worth of space. Though VirtualWisdom isn’t thought of as a storage capacity monitor, by watching for I/O activity, you can easily find opportunities to reclaim unused LUNs.

Below is a step-by-step process with screen grabs to illustrate exactly how this is done.

Start your VirtualWisdom Views client, which is the administration interface for VirtualWisdom. The Views client allows you to configure VirtualWisdom, create reports, set alarms and monitor the data collected by VirtualWisdom. Since we are looking for I/O traffic to a LUN, use the SAN Performance Probe to monitor the frames/sec metric in the SCSI metric set; the screen shot is below.

Then select the LUN and storage fields.

Sort the data first by Frames/Sec then Storage and LUN, via the Data Groupings tab.

Then, in the “data views” tab, select the Summary Table to list out each LUN, and a Trend chart to show the peak data for each period. The Trend chart is important because the Summary Table will show the average for a period. It’s important to note that such a small value over a long period could average out to zero. The Trend chart will let us spot these values.

Go to the reports tab in the views client. Set a period, say 30 days, and generate the report. For our small test lab, you can see that our tool found one LUN with zero activity in 30 days. With the SAN Performance Probe it’s easy to inspect the LUN and figure out why it hasn’t had any traffic.

You can use the same report with different selection criteria to look for underutilized LUNs. It’s easy, quick, and the ROI can be substantial. For a short video of this VirtualWisdom use case take a look below: