Review: A Look at EqualLogic's Technology

Dell already has its own line PowerVault storage servers and a storage partnership with EMC. It seemed like a good time as any to check out the EqualLogic PS3900VX storage array and see what Dell will be able to offer its partners as a result of this deal.

The verdict: EqualLogic has always been a channel-friendly product and that hasn't changed. And with Dell's assurance that the EqualLogic brand would be a separate part of the business, away from direct-sales, the channel will continue to have access to a powerful and flexible storage solution for their customers. (Potential channel conflict fears in the VAR channel notwithstanding.)

EqualLogic introduced this SAS array in February 2007 -- with other competitors also launching rival offerings in the first half of last year in a segment with historically long refresh cycles. The third storage product in the company's PS300 line, the PS3900VX doubled its storage capacity to 4.8 Tbytes, compared to the 2.3 Tbytes available on the earlier PS3800VX storage array. The 3900 chassis can hold up to 16 Seagate Cheetah enterprise drives that spin at 15000 rpm. As fast as Fibre Channel disks, these are 300-Gbyte SAS hard disks. The array also has LSI Logic chipsets inside.

EqualLogic designed its SAN-based products to be budget-friendly while still capable of high storage requirements. Enterprises most commonly have SAN with Fibre Channel because of its speed, despite its high price tag and management complexity. There is also a perception amongst many that SAS, like the even cheaper SATA, does not perform as well as Fibre Channel. EqualLogic launched its PS3000 line, storage arrays capable of high-demand applications such as databases or messaging and collaboration platforms, to offer a viable alternative to Fibre Channel.

With the deal, Dell gained five 7,200 rpm SATA storage arrays, ranging in size from 1.75 Tbytes to 10.5 Tbytes, the 4.8 Tbyte 10,000 rpm SAS array, and two 15,000 rpm SAS arrays. The PS3900XV is the high-end product in this portfolio.

The PS3900XV in the Test Center lab has fully redundant and hot swappable drives with two spares, three gigabit Ethernet interfaces, and 2-Gbytes of battery-backed mirrored memory. The enclosure has its own monitoring system that performs system health checks for component status, disk drive health, and temperature. If a drive starts to fail, it's swapped out of service with a spare. With the new drive active, a RAID rebuild automatically initiates. As soon as the rebuild is complete, the system is back, as good as new. The admin finds out about this because the system automatically sends an e-mail -" the only thing left to do is to physically go back to the chassis and remove the bad drive and put in a new drive as the new spare. The system also has redundant controllers, power supplies, and fans.

If one fails, the other is ready to kick in. There is a mirrored write-back cache with 72-hour battery backup. There are other software tools that automatically check for bad bytes and the integrity of the data already written on the drives. All these extra safeguards are reassuring for reliability.

After hooking up the storage array to the network, the installation software easily detected the hardware address of the box and its associated IP information. It was easy to enter networking data, such as groups and users, into the wizard. After the array was installed and configured, all maintenance and further configuration was handled through a management interface.

The SAN's entire storage capacity is divided into different sections, and applications are assigned as needed, to specific "pools" of data. The pools can be application specific, or allocated to a particular department. The storage can be created using RAID 5, RAID 10, or RAID 50. For the host interface, any standards-compliant iSCSI initiator can be used. The test server running Windows Server 2003 had Microsoft iSCSI Initiator that worked just fine for this purpose. The iSCSI Initiator on the servers just needs to know the target name for a pool so that it can point to the SAN and find the appropriate storage space.

The interface encourages flexibility. New arrays can be added at any time to expand storage space. Applications can be moved from one storage pool to a different -" perhaps, larger -" pool without switching services off. Creating a pool takes mere minutes and can be done on an as-needed basis, instead of trying to predict storage needs ahead of time. Switching RAID functions can be done on the fly.

The interface has a very straightforward way of defining alerts, whether it's to let the admins know a drive has been hot-swapped, to give periodic updates on which drives are filling up, or to provide general usage information.

Thin provisioning uses virtualization to show the application the total amount of storage allocated, while actually allocating a much smaller number of physical storage. As the application needs more space, more space is freed up from the general storage pool. The PS3900XV handled this in a very automatic manner. A 100 Gbyte storage pool (using RAID 5) was created and formatted for use. According to the management console, the pool was using less than 50 Mbytes of actual storage space. From the Windows server, the drive looked like 100 Gbytes. After copying over 30 Gbytes of files, the management console reflected the proper increase in storage to accommodate the files.

The PS3900XV also automatically load balances between storage devices. There is no need to go into the management console to try to redistribute how the data is being written. Despite simultaneously running multiple tests of copying 30-Gbyte data, there was no need to intervene to adjust the workload.

On the physical front, it's not very different from other SANs on the market. Weighing in at a little over 77 pounds, it's a standard 2U chassis. It is a little noisy, but once the door to the rack was closed, it melted in to the general background noise.

The Test Center found the technology to be solid and with potential to deliver significant value. But with so many questions regarding Dell's channel program left to be answered, it is staying off our recommended list -- for now.

So there you have it. It's a flexible storage solution that doesn't require Fibre Channel infrastructure or know-how. For solution providers leery of Dell, the company has said EqualLogic will remain a channel brand. The PS3900XV brings a high-end SAN product to non-enterprise customers at the fraction of cost and difficulty that comes with enterprise storage.