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Dell adds clustered NAS to PowerVault for 'unified' storage

Dell begins integration of its Exanet clustered NAS technology with its PowerVault SMB product—but does the NAS-iSCSI offering qualify as unified storage?

Dell took its first step in integrating Exanet clustered NAS technology into its storage platforms today by adding the Exanet file system into its PowerVault NX3500 small- to medium-sized business (SMB) storage system.

The NX3500 works with the PowerVault MD3600i 10-Gigabit Ethernet (10 GbE) iSCSI system, allowing IT managers to handle file and block data from a single storage pool. Dell is calling the Exanet technology the Dell Scalable File System.

Dell calls this unified storage, although the NX3500 and MD3600i remain separate products managed through separate consoles sharing common storage.

The vendor is starting on the low end with the NAS IP it acquired by purchasing Exanet’s assets in February 2010. Dell’s roadmap calls for it to add the Scalable File System to its EqualLogic midrange iSCSI storage area network (SAN) arrays around mid-year and eventually to its Compellent Fibre Channel SAN systems.

Is this unified storage?

There is no shortage of unified storage systems—also known as multiprotocol storage—already on the market, and most of them such as NetApp’s FAS platform and EMC Corp.’s VNX and VNXe series support block and file in one box with one management console. Scott Sinclair, Dell’s product manager for NAS and file storage, said keeping the file and block capabilities separate in PowerVault improves performance.

“From an architectural standpoint, there are a number of ways to implement unified storage,” Sinclair said. “We are doing something different. We separate the processing and memory to enable better performance. There is a separation between the file process capability and the SAN capability. The goal is to ensure the file demand does not minimize the SAN performance.”

John Webster, senior partner and analyst at Evaluator Group, said not all unified storage is created equal. “There are as many definitions of unified storage as there are products that are called unified,” he said.

In a recent blog post on the Evaluator Group web site, Webster cautioned storage managers to look closely at a unified system’s architecture before buying.

“Storage vendors have come to market with very different implementations of ‘unified’ storage and you have to look under the covers to make your own determination,” he wrote.

Webster added in his blog, “A truly unified storage system provides a single user interface to manage both block and file system storage when the array is installed and later on in production.”

The Dell system doesn’t seem to meet that definition now, although Sinclair said the management consoles for the NX3500 and MD3600i will eventually be combined. For now, the NX3500 management console is the Dell PowerVault NAS Manager GUI and a command line interface, while the MD3600i employs the Dell Modular Disk Storage Manager, which uses a Java-based interface and has multipath failover management of redundant data paths between the server and storage array.

“For this release, there are two different interfaces that operate and look in a similar fashion,” Sinclair said. “In the future, we expect to converge those into one management tool.”

Brett Roscoe, executive director of Dell Data Management, declined to say if there will be integration between the systems’ controllers.

“I don’t want to comment too far into the future,” he said. “We don’t want to sacrifice performance. But as [processor] cores continue to double and triple, there may be a possibility we might converge it.”

Scalable file system first of several Dell storage additions

The Dell Scalable File System presents a storage pool as a single file system and IP address to the clients. Dell paid $12 million for the technology, dropped a reported $150 million on data reduction startup Ocarina Networks and paid $820 million for Compellent later in 2010.

Roscoe said besides integrating the scalable file system into the EqualLogic and Compellent systems, it will add Ocarina’s primary data deduplication capability into its storage platforms.

The PowerVault NX3500 works with the Dell PowerVault MD3600i and MD3620i arrays to scale to 192 TB of raw capacity with SAS, nearline SAS and solid-state drives (SSDs). Dual controllers operate in an active-active environment mirroring each other’s cache. Each controller has two 1 GbE ports for front-end CIFS and NFS connectivity and two 1 GbE ports for back-end iSCSI connectivity.

The Dell MD3600i comes in single or dual controller configurations. Each controller has two 10 GbE iSCSI ports. The 3600i uses 3.5-inch drives and the 3620i has 2.5-inch drives.

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