Using VirtualWisdom to Reclaim Unused Disk Space

Best Practices, LUN, SAN performance storage i/o bottleneck, VirtualWisdom No Comments »

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:

Use LUN Nicknames in VirtualWisdom to Identify VLUN SymmDevice Names

awk, How to, LUN, Nickname, Symmetrix No Comments »

When some customers look at the output of our Hardware Probes such as the 8g FC8, and they’re confirming that all their Oracle transactions are meeting the SLA of 8ms, the LUNs they see are a bit unusual. They’re used to seeing LUNs such as LUN32, LUN33, but VirtualWisdom shows them LUNs like 17652, and they just don’t match up. This hinders the utility of the data, and may reduce the confidence they have in the data itself. When data drives decisions, we need accuracy and we need to be as easy to use as we can based on what we have available on the FC link.

The truth of the mismatch is that the devices involved actually convert the LUN numbers: where Virtual Wisdom shows you “17652″, that’s actually the LUN “on-the-wire”. The actual LUN in the SCSI frame is that large number, but vendor-specific tools convert it to manageable, familiar numbers — which can make the actual LUN appear “wrong”. Although it’s very simple to say “VirtualWisdom isn’t making the same conversion as your vendor-specific tools”, we’d rather be more helpful. When you have a problem on your SAN, “VirtualWisdom doesn’t support…” offers no help towards fixing the problem. Rather than “17652″, we’d rather tell you “Symm Device 1E2B”, which — for a very important customer of ours — is a comfortable middle-ground in identifiers and terms for the LUNs.

So how can we get a usable label on those LUNs? How do we do the lookups for you so that in an emergency, you have the details you need, already dereferenced?

As you’ve seen in the articles I’ve posted, I’m a Field Application Engineer for Virtual Instruments, and making this conversion — plus automating it — are the challenges I enjoy working on and sharing. This how-to article shares how to get SymmDevice aliases mapped onto LUNs as nicknames in a scriptable method. Let’s dive in:

Process Overview

For this process, our flow will look like the following:

In this diagram, the “sysinq” command is used to generate the “sysinq.txt” file; that part of the process is quite dependent on the tools available on your servers, hence shown dotted.


We at Virtual Instruments have witnessed this odd mismatch in LUNs for some time, and initially we just said “Subtract 0×4000″, but that didn’t work precisely. In another instance, we found two servers with a very similar number, so the informal rule became “subtract 17506″, but we later found that this rule was unusable outside that customer. Recently, in very detailed discussions, a customer found the logic that gets them to their LUN Nicknames, as follows:

The “sysinfo” file looks like this: (mocked-up example from testcases)

disk 1071 8/0/12/1/ sdisk CLAIMED DEVICE EMC SYMMETRIX
lunpath 1071 8/0/12/1/0.0x50060482d5123456.0x4392000000000000 eslpt CLAIMED LUN_PATH LUN path for disk6219
disk 1071 8/0/12/1/ sdisk CLAIMED DEVICE EMC SYMMETRIX
disk 1071 8/0/12/1/ sdisk CLAIMED DEVICE EMC SYMMETRIX
lunpath 1071 8/0/12/1/0.0x50060482d5123456.0x4392000000000000 eslpt CLAIMED LUN_PATH LUN path for disk6219
lunpath 1071 8/0/12/1/0.0x50060482d5123456.0x4392000000000000 online

The key part of this file is the line that says:

lunpath ...0x50060482d5123456.0x4392... disk6219

In this case, “50060482d5123456″ is the storage device’s WWN, and 0x4392 is the LUN (17298 in decimal) we detect as the actual LUN used in the SCSI exchange for disk6219.

The “syminq” file looks for a certain server like this: (again, mocked-up example from testcases)

/dev/rdisk/disk6219 R1 000190102037 5773 3701E8B000 2096640
/dev/rdsk/c23t1d2 R1 000190102037 5773 3701E8B000 2096640
/dev/rdsk/c43t1d2 R1 000190102037 5773 3701E8B000 2096640
/dev/rdsk/c133t14d5 R1 000190102037 5773 3701E8B000 2096640

The key part of this file is the line that says:

...disk6219 ...3701E8B...

That rdisk entry is as follows: (keep in mind, the content is replaced by bogus values: some common values may not align anymore)

  • /dev/rdisk/disk6219 is a local device node on the host
  • I’m not sure what “R1″ stands for
  • 000190102037 is the Symmetrix serial number
  • I’m not sure what “5773″ means (model number?)
  • 3701E8B008 breaks down as:
    • 37 — last two digits of serial 000190102037
    • 0 — not sure
    • 1E8B — the SymmDevice ID
    • 000 — Director port number
  • 2096640 (2^21 -512) means the LUN has capacity ~2TB

I don’t have official information, but it’s possible that 01E8B is actually “Symmetrix device 01E”, and “Director #8B”. 0x8b larger than 16 used to mean Processor B, but that seems a bit outdated now. The tools we use could easily give out 5-digit SymmDevice-XXXX values if we could confirm this numbering breakdown.

Essentially, the SysInfo2LUNNickname.awk script does the following:

  1. pre-loads a syminq file to provide “better” nicknames where possible
  2. parses the sysinfo to realize nicknames, substituting syminq results where possible
  3. Output the results as a new-style (VirtualWisdom v2.1 or later) nickname CSV

The resulting nicknames.csv has a series of lines such as:


As you can see, where there is a “better” match, “SymmDevice-1E8B” is used; otherwise, “diskXXXX” is still there. At this particular customer, “1E8B” is an example of a common name for their LUNs rather than the 17298 reported by VirtualInstruments or the 0×4392 reported in hex.

For exceptionally large syminq files, because gawk.exe is loading up a large associative array, memory usage may temporarily peak; this has been tested on 500k – 1MB text files without visible adverse effects, but hidden memory usage such as interpreters’ associative arrays and implicit memory-management is something to be aware of.

Running the Script

gawk.exe -v SYMINQ=syminq.txt -f SysInfo2LUNNickname.awk sysinfo.txt > nicknames.csv

It’s that simple. In order to improve re-use, I collected this logic as the AWK script because I’ve never had portability problems with AWK except for the UNIX/Windows CR/CRLF/LF text line-endings debate.

The script is non-interactive, but prints the results, so the script is typically run with the output redirected to a file. Running it is very quiet, as you’d expect:

gawk execution screencap showing LUN Nickname creation

Complete Example

A complete example is difficult for this how-to because the files used are scattered on each server; collecting the sysinfo, and the syminq output from each server may be the more difficult part. My test example looks like the following (I always recommend using full pathnames for tools):

@echo off
cd VirtualWisdomData

REM following is all on one line but split here for easier reading
-v SYMINQ=sandatasyminq01.txt
-f sandataSysInfo2LUNicknames.awk
sandatasysinfo > VirtualWisdomDataDeviceNicknamenicknames.csv

Similar to previous Nickname-generation/derivation tutorials, this process generates a single nicknames.csv file. You could append this result to any other generated file for which you already have an import schedule, or create a new one. In order to be as complete as possible, I’ve included an import schedule example that should be surprisingly similar to the others (and similarly brief: the User Guide has more detail regarding Schedules)

  1. Views Application, Setup tab: Views Application, Setup Tab
  2. “Schedules” page, roughly 5th item down: Views Application, Setup Tab, Schedules page
  3. Create a new Schedule, with the action “Import WWN Nicknames”: (or, if you prefer, “Import LUN Nicknames”) Views Application, Setup Tab, Nickname Import Schedule
  4. …and configure it to use a new WWN Importing Configuration, as follows. NOTE we only use a local filename, all files are in the DeviceNickname directory of your VirtualWisdomData folder:Nickname Import configuration, nicknames.csv
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