The storage industry has spawned more than its fair share of acronyms with NAS (network attached storage) and SANs (storage area networks) always in the spotlight and touted as the ideal solutions for companies struggling to keep up with the demand for more and more data.
You should add DAS (direct attached storage) to this list as it offers the simplest, and frequently the most cost effective, method of adding more storage to the network. Much more than just dumb disk boxes, DAS systems can be highly sophisticated. The latest R31610 chassis provides room for up to sixteen of the latest Serial ATA (SATA) drives and teams them up an integrated RAID controller supporting RAID-0, -1, -0+1, -3 and -5 arrays.
This 3U chassis offers an impressive range of features with a SATA 150 backplane which supports hot-swap and hot-standby drives. Redundancy is very high on the agenda as three 300W hot-swap power supplies are included. An internal monitoring system keeps a close eye on them and also implements load balancing across all units. Above these are a pair of blower fans that are also hot swappable in the event of a failure. At the top are enclosures for the SCSI and RAID controllers. Monitoring hardware which can be easily removed and replaced once the system is powered down. The RAID controller is built around a 100MHz Intel 80303 64-bit RISC processor and comes supplied with a healthy 128MB of cache memory that can be upgraded to a maximum of 512MB.
The sixteen bays are easily accessible at the front and the review system came endowed with a quad of the very latest 250GB Western Digital Caviar WD2500JD SATA hard disks. Below the drive bays is a neat control panel and LCD status window that can be flipped down out of the way to provide access to the drives. From here, you can view environmental details such as temperatures, monitor drive and cooling fan status, and configure the system. Three serial ports are provided with one supporting an intelligent UPS while the second is used to connect a modem for sending out failure alerts via pager or fax.
Installation is the weakest area of any DAS devices, as they are connected directly to the host system which, obviously, must be powered down during this phase – a problem that doesn’t occur with NAS appliances or SANs. However, due to its simplicity, this process won’t take long as all you do is configure your arrays first and then link the chassis to a suitable SCSI adapter. The SCSI controller in the R31610 provides dual Ultra160 channels and allows two hosts to connect to the system and use separate disk arrays, if required.
The next phase was a big disappointment as configuration can only be run from either the unit’s own control panel, or via a serial port connection and a HyperTerminal session. Either way, the menu system is crude and awkward to navigate and the documentation overly simplistic, making it difficult to create RAID arrays or even view their status and which disks are being used.
A third option is a browser interface loaded on the host system, which uses a utility to query the chassis over the SCSI connection. Alas, we were advised by Westek that at the time of writing this utility did not currently support the SATA version of this chassis and was in the process of being updated.
For testing we used a Pentium III 1.13GHz system running Windows 2000 Server and equipped with an Adaptec 39160 Ultra160 host adapter that was used to connect it to the disk array. With the R31610 in action all we saw on the host system was a new drive that could be partitioned, as required, from the Disk Management tool.
Overall, Serial ATA appears to have the measure of SCSI and this disk array chassis proves the point by delivering all the features you’d expect from a RAID system. Apart from the cumbersome configuration routines, it backs this up with an excellent level of features and good performance.
There are plenty of choices for improving your storage outlook but picking the wrong one could be a costly mistake. The DAS option may not be as sophisticated as the NAS appliance but if you’re looking for the fastest and most cost-effective method of expanding disk capacity then it’s hard to beat.