NEC Solutions 2500 Storage Array

NEC's S2500 Storage Array has much to recommend it to businesses that value flexibility in their storage environments. Similar in architecture to EMC's Clariion CX500 but with a lower price and faster host connections, the S2500 lets you build dynamic RAID sets to which you can add drives for growing storage requirements.

The S2500 squeezes a pair of active-active redundant RAID controllers, each with 4 GB of battery backed-up cache, a pair of redundant power supplies and 15 Fibre Channel drives into a 3U rack-mount enclosure. If you need more than the 4.5 TB of disk space you can cram in the base cabinet, you can add up to seven drive cabinets for a total of 120 Fiber Channel or lower-cost, higher-density SATA drives, or a combination of the two.

Everybody In!

You can build fixed-size RAID sets (pools, in NEC lingo) using RAID 1, 10, 5 or 50, or any combination of these. Most vendors only give you the option of static pools, but NEC goes one better with support for dynamic pools using RAID 6. It's a lot easier to manage your disk space using dynamic pools: If you need to expand the logical drive for an Exchange database on a static RAID set, you must have enough free space in that RAID set or move that drive to a RAID set that does. With a dynamic pool you simply add one or two new drives to the pool, creating space for expanding the logical drive. You can find a similar feature in some storage products from Hewlett-Packard and Xiotech, but it's still relatively rare.

I'm a fan of RAID 6, which uses no more disk space than RAID 5 with a hot spare and adds only a small write-performance penalty if it's implemented well. Because RAID 6 writes parity information to two drives, your data is protected in the event of a disk failure. With today's 400 GB and larger drives, it can take several hours to rebuild an array on a hot spare, during which time your data is at risk if there's a second drive failure. RAID 6 support also provides some peace of mind for those worried about the reliability of SATA drives. Of course, global hot spares are supported for those who want them.

The S2500 has the hot new thing in the Fibre Channel world: 4-Gbps Fibre Channel ports, two on each controller for host access. NEC is ahead of the competition on this front, as EMC's Clariion CX500 and HP's EVA6000 haven't yet been upgraded to 4 Gbps. As expected the 4-Gbps ports automatically adjusted to the lower speed when I connected 1-Gbps and 2-Gbps switches and host adapters.

On the back end, there are two 2-Gbps Fibre Channel loops using HSSDC (high-speed synchronous differential connectors) copper connections. One loop is dedicated to Fiber Channel enclosures and the other can be used for Fibre Channel or SATA enclosures.

Lift and Set

I got a couple of the stronger lab assistants to help me mount the burly S2500--it's well over 100 pounds--in a rack, and hooked it into Network Computing's Purchase College (SUNY) partner labs' Ethernet (for management) and Fiber Channel SAN. The management PC Ethernet port on each controller has a fixed 10.1.0.11 IP address. I set a PC to an address in that subnet, pointed my browser at the array, and used the Web interface to set the IP address on the general management port. I then installed the NEC Storage Manager server and client components on a server and spent about an hour attempting--and failing-- to manage the array. A call to NEC revealed that the IP address change wouldn't take effect until I turned the power to the array off and on. Ah-hem.Like its competitors, NEC will be glad to sell you software upgrades to add such features as snapshots, internal and remote replication, and performance analysis. NEC takes this a la carte pricing perhaps a step too far, charging for access control (LUN Masking) to limit access to logical drives to specific servers and for connections to the S2500. Prices for these options range from $1,400 for multipath support to $17,000 for replication. Luckily NEC sent us licenses for all the available options.

Forget the Stress

Using the Storage Manager GUI, which runs on Windows and Unix/Linux hosts, or command line tools, I created a storage pool and logical drives. Here I ran into a snag; when I tried to enter the WWNs (World Wide Names) of my eight servers to allow access to logical drives for performance testing, the S2500 wouldn't allow me to add more than the four for which I was licensed. Four PC servers with 1- and 2-Gbps Fiber Channel HBAs just can't generate enough disk I/O to really stress an array in this class. It's worth noting that the S2500 turned in impressive performance even while being accessed by four Windows servers at the same time. It should easily handle multiple Exchange, SQL Servers or similar transactional applications in a production environment.

Perhaps the S2500's biggest weakness is its documentation, which didn't stand the test of translation from Japanese into English very well. Stilted language and an overuse of two-letter acronyms make it difficult to absorb the concepts.

But a good VAR or strong coffee can get you through the manual. And at the end of the day, you'll have in your hands a storage array that can be optimally configured to meet your business needs.Howard Marks is founder and chief scientist at Networks Are Our Lives, a network design and consulting firm in Hoboken, N.J. Write to him at [email protected].