LapiStor DiscPac DPa-5316s-320 review
The review system came equipped with a full complement of 120GB Seagate Barracuda hard disks in solid hot-swap carriers and converts these to dual-channel Ultra320 SCSI operation. It’s worth mentioning that although the drives supplied are the slower SATA/150 models, they do support SATA Phase II NCQ (native command queuing). This aims to improve performance for non-sequential I/O operations by taking multiple requests for disk operations and reordering them so they’re executed more efficiently.
For a DAS appliance, the 5316s offers an impressive range of features. The Areca RAID controller is well specified and supports the latest RAID6 arrays. These require a minimum of four drives to function, as they use the capacity of two for redundancy, but the bonus is that they can survive the loss of two drives. Online capacity expansion allows you to add more drives to a volume set without taking the array offline. Array roaming stores the unit’s configuration on the disks as well as NVRAM. So, if the appliance fails, you can shift the drives over to a new box, fit them in any order and all the RAID information is available to the new controller. You can also start off with a small number of drives and, as you add more, migrate them online from a RAID1 stripe to a full RAID5 array.
Installation is simply a case of inserting the drives, connecting the appliance to a server and powering everything up. Management options abound, as there’s a front-mounted LCD and keypad, while the RAID controller sled at the rear has a serial port for a VT100 terminal emulation session, plus a Fast Ethernet port for web browser access. We found the front panel the least intuitive, but it does allow you to create and expand RAID arrays, define volumes and view system operations and environmental information.
For testing, the appliance was linked to a dual-Xeon Windows Server 2003 system. We connected the disk array to a dedicated Adaptec Ultra320 PCI-X controller card. The system came preconfigured with 15 drives in a RAID6 array, with one acting as a hot spare. We opted to use the web interface to configure volumes, as we found that although it’s a tad rudimentary it was the easiest of the three methods to use. Performance is impressive. With Iometer (www.iometer.org) configured for 64KB sequential read transfer requests, ten outstanding I/Os and two disk workers, we saw the server’s internal Ultra320 hard disk return a modest 53MB/sec throughput. Running the same test on a 50GB volume configured on the appliance’s default RAID6 array saw this increase to 123MB/sec.
With all the hype surrounding SANs, iSCSI and NAS appliances, it’s easy to forget that DAS is often the easiest and best-value solution for increasing server capacity. The DiscPac 5316s delivers plenty of storage for the price, offers an impressive range of RAID capabilities and backs these up with enterprise-level features such as online capacity expansion.