VTrak makes the leap to SANs easy

Small and medium businesses’ most serious fear when exploring networked storage is that of being sucked into a complicated, expensive, and difficult-to-manage solution. That concern often proves too pessimistic but is nevertheless justified by the complex administration and boutique prices that characterize many SAN solutions.

It’s no surprise, then, that small companies have generally stuck to the easier-to-navigate waters of server-attached storage rather than venturing into the world of SANs. As more vendors offer SMB customers less expensive and easier-to-manage SAN arrays, those concerns are fading.

The VTrak 15200, a recently released iSCSI array from Promise Technology, is one such user-friendly product that combines ease of use and good performance with an attractive price. 

In addition to offering good capacity, sturdy construction, and easy administration tools, the VTrak 15200 also bridges the gap between DAS and SANs with a modular architecture that can easily switch from SCSI to iSCSI connectivity, which makes the unit especially attractive for networked storage newbies.

Not Rocket Science

VTrak 15200’s redundant components and modular structure are easily taken apart without using any tools and without powering off. The back of its 3U box is a mosaic of easily replaceable modules, including a dual fan assembly, dual power supply, and one processor and one I/O controller module.

The 15200’s standard I/O controller mounts two iSCSI ports, plus a serial port and an Ethernet port for CLI and GUI-based administration. One of those modules will host up to 512 MB of automatically saved, battery-protected cache.

Along with this standard controller, Promise offers a compatible SCSI controller that transforms the 15200 into a DAS array, which facilitates connection to any server mounting a recent SCSI adapter. With an easy update (essentially replacing the SCSI module with its iSCSI equivalent), the same array can be promoted to networked storage without data corruption.

The front of this 19-inch, rack-sized unit has room for 15 SATA drives, vertically mounted and easily removable, thanks to smoothly-sliding disk carriers. After I mounted 15 Western Digital WD740 drives, the unit capacity was just a notch above 1TB; for additional capacity, you can mount larger SATA drives or, using proper adapters, less expensive parallel ATA drives.

Mimicking a DAS environment with the VTrak was easy: I slid in the SCSI controller and ran a cable to an Adaptec Ultra160 SCSI adapter mounted on my HP Proliant ML350 server. The array’s two existing LUNs (logical unit numbers) were immediately recognized and subsequently became part of the storage capacity of my Windows 2003 machine.

After partitioning and formatting, I copied some files to those two volumes, then powered down to convert my DAS array to networked storage. I replaced the 15200’s SCSI controller with its original two-port iSCSI module. Then, using the array’s CLI-based management tool, I set those iSCSI ports to IP addresses consistent with my network.

To add iSCSI connectivity to my server, I mounted a QLogic QLA4010 HBA and installed its drivers and the SANSurfer Control management application from Promise’s CD.

I connected my HBA to one of the array ports via Ethernet cable, and my simple SAN was ready. Shortly after typing the 15200’s IP address into SANSurfer, the two LUNs appeared in my server volumes with their file content intact. Converting the VTrak from SCSI to networked storage was easy and took only a few minutes.

SAN Admin Aid

If you are not quite ready to jump on a SAN but expect to make the leap soon, the VTrak 15200’s SCSI controller insures a smooth transition that will preserve your existing investment and eliminate long data transfers from old media.

I was satisfied with the array’s administrative tools, including CLI — reachable via serial port or via Telnet — and WebPAM, a browser-based GUI. WebPAM offers only a subset of the CLI functionality and isn’t the most sophisticated GUI, but it covers the basics of daily administration, enabling the same client to point to multiple VTrak arrays.

Using WebPAM, I created and deleted LUNs and remotely monitored the status of the enclosure. You can also define multiple users and restrict access to some critical features, such as destroying a LUN. More sophisticated tweaking, such as setting the IP address for the iSCSI ports or changing cache policy, are possible only from the CLI.

Other management tools may overtake WebPAM in a head-to-head feature comparison, but its simplicity is exemplary enough to make even a rookie storage administrator comfortable.

I found that with the proper configuration, you can squeeze pretty good performance from the VTrak array. To obtain the best performance, I started a new configuration, spreading a single RAID 5 LUN over 13 drives and leaving two spares.

I launched the same server-load simulation script on two machines and saw Iometer measure an aggregate 900 I/O operations per second. With a script simulating a restore process with high block size, the Iometer gauge came near 96MBps, close to the theoretical speed of the connection. 

Repeating the same run on a similar server but without the QLogic HBA, Iometer measured a slightly lower transfer rate. However, the CPU jumped from less than 2 percent to more than 30 percent. The lesson? If you plan to squeeze top performance from the VTrak, plan on installing a TCP offload engine such as the QLA4010 on your busiest, if not all, servers.

After putting it through its paces, the VTrack 15200 struck me as a well-engineered, solid-performing, easy-to-manage array that can stretch its reach into the familiar DAS environment. For many small datacenters that combination may be irresistible — and the price is right, too.