EMC goes virtual

Virtualized storage is hardly new, but it has been reinvigorated by interesting solutions from major vendors, such as Hitachi's TagmaStore and IBM's SAN Volume Controller.

You can now count EMC as a member of that crowd, thanks to the recent launch of Invista, its new virtual storage solution. Invista offers a rich set of features that take advantage of the powerful capabilities of intelligent switches from Brocade, Cisco, and (in the future) McData.

Although increased efficiency and more effective administration are the more obvious benefits of storage virtualization, vendors have discovered that indirect addressing of a LUN (logical unit number) -- a key prerequisite for virtualized storage -- allows for managing of foreign arrays as seamlessly as their own.

I had an early experience with Invista at one of the EMC labs, and it gave me a pretty good idea of what the product has to offer. Invista brings an unrivalled level of simplicity to managing EMC storage; administration tools make previously unthinkable feats possible, such as moving a LUN without disrupting running applications or easily migrating data across different arrays.

Understandably, both vendors and customers are intrigued by the new possibilities offered by storage virtualization, because it can extend the life of existing assets. That's music to the ears of many CEOs, and considering that a single storage box can cost more than Invista (which starts around $300,000), EMC's virtual storage solution plays a tantalizing tune.

The virtual crew

Invista's applications run on intelligent switches located between storage arrays and hosts. On the array side, Invista simulates the behaviour of a storage-hungry server; on the host side, it plays the role of a large storage array.

My test bed included LUNs from Symmetrix and Clariion boxes, as well as application servers running Windows Server 2003, one of which doubled as the management station for my virtualization activities.

My Invista instance included two CPCs (Control Path Clusters) -- essentially two resilient servers running the Element Manager virtualization software -- with local disk space to permanently store virtualization metadata and the EMC software for the two intelligent switches.

Intelligent switches are an essential component of Invista. They do the actual directing of virtualized traffic according to the EMC code they run and the metadata and tables defined by Element Manager. The intelligent switches are an open platform, able to run storage applications developed by other vendors. A minimum of two intelligent switches is required in a resilient configuration; my configuration had two Connectrix (Brocade) AP-7420B switches.

Invista's management tool is a Java-based GUI that runs either as a stand-alone application or inside a browser window. Invista also has a friendly and comprehensive CLI with extensive online help, an obvious choice for scripting virtualization tasks.

The Invista GUI offers the same functionality as the CLI wrapped in easy-to-use wizards, but adds an intuitive tree view of physical and virtualized resources that simplifies monitoring and administration.

Lining up virtual ducks

I was immediately comfortable with the Invista GUI, and quickly learned how to create logical volumes by allocating storage from storage elements (in essence, LUNs), and how to group homogeneous virtual resources in virtual frames.

One of Invista's more interesting virtualization features is the ability to move a logical volume from one storage device to another without interrupting applications that are using that volume. With-out virtualization, moving a volume often means stopping the application, moving the volume, then restarting the application and changing it to look at the data's new place. None of this is necessary with a virtual volume.

To simulate moving a volume while an app is running, I created a virtual volume from a Clariion storage element, assigned the volume to my host, and filled it with files. Among those files was a movie clip that I kept running.

Back at the Invista console, I clicked on the new volume and chose "move"; Invista asked me to choose a target location and a data rate for the move (allowing for either low network load or faster completion). The move went off without a hitch, and the movie clip never experienced a hiccup -- a good indication that even the most demanding application should not be affected in such a transfer.

Invista's powerful virtualization simplifies some administrative tasks, such as moving data to a faster array, without painful disruptions to your business. This alone should justify the nontrivial investment needed to acquire Invista.

But there's more. For example, you can clone a volume and create a constantly updated mirrored image that can be detached and assigned to a different task (development, data mining, backups, and such) at any time.

Invista also has powerful features to create new virtual volumes and dynamically extend one that's running out of space. For the latter to be useful, however, your server OS must be able to play along.

Preserving current data is another concern. Invista can import existing volumes into a virtualized environment without affecting the data. This is a must-have for a smooth and painless installation.

To mark the difference in performance, I measured the transfer rate with Iometer before and after importing the volume. Adding the non virtualized LUN to my Windows host, formatting a volume, and filling it with data was nothing new. After running Iometer and saving the test results, I added the LUN to the zone managed by Invista.

With the new zoning complete, I clicked the rescan button on the Invista GUI. The new LUN appeared immediately in the tree, and I was able to assign it to my server as a virtual volume. As expected, the data content of the volume was unaffected.

Running the same Iometer script on the imported volume showed no significant difference in transfer rate, compared with the test run on the non virtualized volume. This result was a sign that Invista's off-band virtualization adds little or no latency to a SAN.

In the zone

After evaluating Invista, my only want is for better integration with EMC's ControlCenter SRM software and other management tools. As it is now, you must switch management consoles when moving outside Invista, for example, to define a new LUN on a Clariion or Symmetrix array, or to change zoning. However, I wouldn't be at all surprised to learn that EMC has already chalked that in for future releases.

Otherwise, Invista storage virtualization brings a much-needed breath of administrative fresh air to existing SANs. It's not quite a free lunch, but it could be your most effective investment toward managing storage according to business needs rather than technical constraints.

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