What's so compelling about Compellent?

That's a question that I asked CEO Phil Soran when he visited InformationWeek offices in San Francisco Oct. 12 and kept asking as Scott Horst, VP of corporate marketing, Scott DesBles, principal storage architect, and Robin Drago, senior analyst relations manager, visited last week as well. The question is simple; the answer is slightly more complicated.

Compellent, from the time it was founded in 2002, didn't deal with data movement at the traditional volume level, where a data set is associated with a given physical set of disk drives, explained Soran. It automated the movement of data on the much smaller block level and provided built-in intelligence for placement of data in a tiered storage system.

The block level is much finer-grained measure, say 512 bytes to 2 MB at a time. The block-level approach allows smaller chunks of data to be retrieved and stored and storage space is set aside more precisely -- below the amount required with a logical unit number (LUN) approach -- with less vacant space created to hold a given data set.

A dataset may reside on a fast set of drives in the morning and a slower set in the afternoon, as demand for it slackens, but the Compellent management system knows where it is in each case. The management interface refers to it with a logical, not physical, identifier, and knows that its status has changed from frequently used to less frequently used. If it becomes infrequently used, Compellent's Enterprise Manager will automatically send it to a new location on slower but more cost-effective drives for long-term storage.

If you don't start out with the idea of discriminating between frequently used and infrequently used data, it's hard to go back and impose that view on your storage software, Soran asserts. But if the system can't do it, you impose the task on the storage administrator. With the masses of data being collected these days, administrators need some automated help. Compellent initially stores all data on the fastest available storage, then in background, and then moves the least frequently accessed to slower storage. As much as 80% will eventually be shifted off the highest tier.

This tiered system doesn't have to await the decisions of a human storage manager and then respond to them. It makes many of them on its own and Compellent has been making brisk headway among mid-sized businesses that can't employ big IT staffs. Third-quarter results, reported Oct. 26, showed a 15% growth in revenue to $42.1 million, an increase in customers from 179 to 2,303, and 55.9% gross margins. It works with a variety of storage vendor hardware and includes built-in scalability. Add drives, and it prompts an automatic restriping of resident data across all drives, picking up parallel disk capacity. Compellent can also create virtual volumes, allowing parallel read/write operations across all drives.

In the same vein, Soran said, Compellent is well positioned to connect to virtual machine systems, which need logical, not physical, storage. Physically attached storage, for example, doesn't easily reconnect when the virtual machine is live-migrated from one server to another. Virtual volumes will work fine, provided the storage system integrates with the virtual machine management system. Heineken Netherlands said during VMworld Sept. 1 that it combined a minimal amount of expensive solid-state disk with low-cost SATA disk drives to achieve the performance it wanted for its HOPS supply chain. (I'm not sure in retrospect that HOPS is an acronym, even if the Dutch beer supplier treated it as one.)

All of this positions Compellent as a supplier of a storage system suitable for cloud computing. It's not the only one. I'm reminded in this discussion of the debate over 3Par and how it also took a thin-provisioning approach in storage. Dell initially bid $1.15 billion for the small storage supplier, then got into a bidding war with Hewlett-Packard, which boosted the price to $2.35 billion. HP ultimately picked up the tab.

On Monday, Compellent announced the 5.4 release of Storage Center, its core product. Live Volume in the 5.4 Storage Center release automatically moves associated storage with a virtual machine being transferred to another server. The VM may be generated by VMware's ESX Server, Citrix Systems' XenServer, or Microsoft's Hyper-V.

Compellent has made use of VMware's storage API to allow Compellent storage to be managed through the virtualization management system of vSphere 4.1, said DesBles in an interview. This tight integration makes Compellent a better fit with the virtualized section of the data center and the future private cloud.

As the data center virtualizes, network I/O, the network itself, and storage will have to keep up. They'll have to fit in with heavily virtualized servers and be capable of providing just the right capacity to virtual machines as they come to life and start working. Given the way Compellent thought through storage issues as it launched eight years ago, that gives it a compelling story today.