With room to grow

expensive investments in storage arrays are often written off — not because of the demise of perfectly functional equipment, but because of the emergence of a new technology twist or the demand for higher capacity. When replacing outdated storage arrays, companies face the additional cost and inconvenience of transferring precious data to the new system.

EMC targets these problems with new Clariion storage arrays targeted at midsize companies. These arrays, which include the CX200, the CX400, and the CX600, combine a more affordable acquisition price with an easy-to-update, modular architecture designed to protect them from early obsolescence.

We tested the Clariion CX400 and found that its modularity is not its only likeable feature. We appreciated its rich suite of software that simplifies management, disaster recovery, and performance tuning, as well as its redundant architecture that promises nonstop operations and unrestricted scalability.

The CX400’s robustness and resiliency are evident at first glance. The basic configuration module is a rack-mountable enclosure — measuring 24 inches deep, 4U tall, and 18 inches wide — that hosts on the front 15 hot-swappable drive bays.

Our single-enclosure unit was fully populated with Seagate Cheetah 73.4GB FC (Fibre Channel) drives, but you can start with a minimum of five drives and add more as capacity demand grows. To maximize speed or capacity, you can choose different drive models; for instance, 36GB at 15K RPM or 146GB at 10K RPM. For further expansion, stack up to four enclosures, add more stacks, or update to a CX600.

On the back of the array are two power-supply and two SP (storage processor) modules. Each SP has an 800MHz Intel Pentium processor and controls data transfers between disk drives, via a 200MBps FC arbitrated loop, and the network, via two 2Gbps FC and two Ethernet ports.

The SPs control storage-volume operations, either individually or preferably in tandem. If one fails, the other takes over with minimal disruption until you replace the faulty module. Moreover, concurrent drives access is automatically balanced across the two SPs.

For increased protection from power outages, the CX400 comes with two standby power supply units (one for each SP) that are essentially battery backups that ensure a graceful shutdown in case of power failure, automatically saving the SP cache content to disk .

It was difficult not to get excited while exploring the architecture of the CX400. Each component is fully redundant and can be replaced without tools and without halting the unit. Also, having battery backup for each SP adds peace of mind that your data will be safe.

You can easily boost capacity and performance by purchasing more drives and additional enclosures, or by lining up multiple CX400 stacks in your SAN. And, the different models of the CX line are fully compatible. For instance, if you outgrow the CX400, you can move its enclosures to a new CX600 stack, preserving most of your hardware investment and avoiding painful and lengthy data migrations to a new storage arrays.

Resiliency, robustness, and quasi-unrestricted expandability are winning points for the CX400. But how easy is it to manage this baby? Administration is done via serial connection or via Ethernet, but using Navisphere, the powerful EMC management software that you can have preinstalled — albeit at additional cost — you will never need access to the serial port of the CX400.

Through Navisphere’s friendly GUI, you can monitor the status of each hardware component of the array, control performance and work loads, and allocate disk space to your servers. Adding SnapView, another application from EMC, allows you to create automatic snapshots of your disk volumes to protect business-critical databases.

Our unit came installed with Navisphere and SnapView, which EMC had configured to work with our LAN (a service that any customer will receive). All we had to do was connect the unit and our servers to the FC switch (a Brocade SilkWorm unit rebranded EMC) and link the Ethernet ports to our LAN.

Pointing our browser to one of the CX400 IP addresses was all it took to access Navisphere. Its Java-based client allows control of one or multiple CX400 units from any computer within HTTP reach. By installing a Navisphere agent on our servers, we had a more accurate view of our storage allocation that made pinpointing the storage resources assigned to each computer easy.

Now it was time to put our CX400 to work. From the Navisphere GUI, we defined a RAID group, a logical container for the disk drives of the CX400, and we assigned physical volumes to be part of that group. Next, we carved a logical volume (a LUN, or logical unit number) from that RAID group and assigned it to our host. We had to reboot our Windows 2000 Server before we could access to the new logical volume. Having to restart the server can be quite annoying if you have other applications running; we’d like to see smoother operations on Windows.

Typically, you allocate to the same RAID group LUNs with similar RAID characteristics: The CX400 will automatically split the allocated capacity over multiple physical drives. If you assign a spare physical volume to a RAID group, the CX400 will automatically recover a failing disk drive, replacing it with the spare unit, without service interruptions.

To test that feature, we started read and write operations on the new volume using Intel IOMeter on our server. The CX400 LED began blinking, showing which physical drives were in use. To simulate a disk failure, we pulled off one of the disk drives. Our server continued to work unaffected. On the Navisphere client, the icon for that RAID group had changed, correctly showing a fault condition. We reinserted the disk drive in its slot and after a few minutes, the CX400 had fully recovered from the failure and restored the spare volume.

We enjoyed working with the CX400. The unit is rugged enough to survive multiple hardware failures, and the management software facilitates making the most of its resiliency to keep the data flowing and your business running.

Neither the array nor its software come cheaply, but the promise of easy deployment, simplified manageability, and excellent scalability make the CX400 the ideal solution for many companies’ storage woes.