Data Centers

Setting up a mirrored LUN with EMC Unisphere

Lauren Malhoit takes you through the basic set up for replicating a LUN to a recovery site using EMC's Unisphere GUI.

A few weeks ago I wrote a blog about setting up vSphere SRM 5.0 with EMC Mirrorview.  Now that's all well and good, but if you don't have a LUN from your protected site being replicated to your recovery site, none of that will work!  A LUN is an acronym for Logical Unit.  It's basically a portion of your storage that has been created on the storage side of things that you can present to servers (in the previous case ESXi servers).  In this blog, I'll take you through the basic set up for replicating a LUN to the recovery site using EMC's Unisphere GUI.  I'll be using some SRM terms like "protected" and "recovery" sites to make things more clear.

I'm assuming you already have a LUN set up that is presented to your ESXi servers that you'd like to replicate.  This would be the LUN that your production servers are sitting on already.  So, at this point, just open a browser and login to the Unisphere GUI where you can find this particular LUN. You should be able to set up Unisphere so that you can see both sites and just click on the site you need to configure according to the following steps.

On the protected side

  1. Go to Storage>>Pools/RAID Groups, click on the RAID Groups tab and find the LUN within the RAID group.
  2. Right click on that LUN and click Properties.
  3. Look at the user blocks under "Capacity" and write down that number for later use.  Make sure you note the exact number of user blocks!

On the recovery side

  1. Highlight the RAID group with enough contiguous storage to support the LUN you're trying to replicate.  Obviously, you'll need the same amount of space on both sides.
  2. Right click that RAID group and click the Create LUN link.
  3. Select the RAID type (ex: RAID 5, you can find an explanation of RAID types here.
  4. Under LUN properties enter the User Capacity that you noted before in Step 3 on the protected side and change the dropdown menu to say "blocks."  Click Apply.

Back to the protected side...

  1. Hover over the Replicas tab at the top and click on Mirrors
  2. On the left side click on the Create Mirror link
  3. Choose the Mirror Type (synchronous/asynchronous - for an explanation of the differences click here.
  4. Name the mirror, for this example I'll just call it SRMmirror1.
  5. Under Primary Storage expand one of the datamovers (spA or spB) and choose the LUN you would like to replicate (the one you noted the User Capacity of earlier).
  6. Now right click on the mirror you just created, SRMmirror1, and click on Add Secondary Image.
  7. As you did in the previous two steps, expand the datamovers on the recovery side this time to find the LUN on the recovery site.  The only LUN that should appear is the one you just created with the exact number of blocks you need.  Select that LUN and click OK.

Back to the recovery side...

  1. Go to Storage>>Pools/RAID Groups.
  2. Click on the RAID groups tab and select the RAID Group where your LUN is.
  3. Right click on the LUN and select Add to storage group.  Move the LUN over to the storage group that will automatically present it to the ESXi servers.

It should start syncing at this point.  Depending on the amount of data and the link you have between your two sites this could take several days or weeks to complete the initial sync.  You can play with the sync settings as well to tell it how often you'd like it to sync and whether you'd like it to sync when the previous sync starts or after it ends.

This is a very basic description of what needs to be done to replicate LUNs using EMC Unisphere and MirrorView.  There are many more configurations that go into setting up storage properly, and especially using MirrorView snapshots (to fully utilize SRM failover testing), etc. I recommend getting help from your storage admin if you have one!  If you don't, I would definitely suggest reading through the various admin guides and consulting with someone knowledgeable on this subject before jumping in head first.

About Lauren Malhoit

Lauren Malhoit has been in the IT field for over 10 years and has acquired several data center certifications. She's currently a Technology Evangelist for Cisco focusing on ACI and Nexus 9000. She has been writing for a few years for TechRepublic, Te...

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