Product Reviews

Since its appearance at the storage circus some three years ago, iSCSI (internet SCSI) has gone from side-show freak to main attraction. Overland Storage has been there right from the start and, with the REO RA2000, it brought one of the very first iSCSI storage appliances to market. Since then, there have been plenty of arguments about where IP SANs fit into the network storage picture. The general consensus now is that for SMBs they make a more cost-effective alternative to overpriced FC (Fibre Channel) SAN products, while at the enterprise level, where performance is a higher priority, they can fit in alongside FC.

The latest REO 4000 brings the best of both worlds. This data backup and recovery appliance delivers support for both iSCSI and FC connectivity, and its hard disks can be configured to emulate tape drives and libraries as well as disk volumes. The appliance can also accept physical tape drives and uses a passthrough mode, which allows them to be accessed as though they're iSCSI targets.

iSCSI technology may have moved on since the days of the RA2000, but the appliance's specification certainly hasn't. It uses virtually the same base hardware as its predecessor, the only difference being the extra dual-port 2Gb/sec FC card. Management access is provided by a single 10/100BaseTX port, while iSCSI targets are presented via a pair of Gigabit Ethernet ports. Storage comes courtesy of eight 250GB Seagate SATA hard disks in removable carriers. Two groups of four drives are connected to separate RAID cards and each quartet is configured from the web interface for RAID functions.

The web interface is easy enough to use. You start by assigning new IP addresses to each data port and providing a couple of email addresses for alert forwarding. Next, you choose how you want the physical drives to be configured. You can opt for two RAID0 stripes or a pair of RAID5 redundant arrays, which are then presented as two logical drives. For performance testing, we selected dual RAID0 arrays. You can create up to 64 logical drives, or LUNs, for presentation as either a virtual disk, standalone tape drive or as a dynamic

In practice, the Overland method works well. We created a range of iSCSI and FC disk targets and had no problem attaching our client test systems to them. Virtual tapes were also easy to create and manage. As soon as we logged the Microsoft initiator version 2.1 software onto the virtual tape target, the client system immediately spotted an LTO-2 tape drive and loaded the drivers for it. You have a choice of three virtual libraries, with a wide range of drive and slot combinations. We created a virtual NEO 2000 library with one drive and 30 slots, which was recognised by Computer Associates' ARCserve without any problems.

So far so good, but our performance tests showed that the REO 4000 has some major issues. We created two 50GB logical disk volumes, and assigned an iSCSI initiator to one and an FC initiator to the other. Using a Supermicro dual 2.4GHz Xeon rack server equipped with Gigabit Ethernet and a QLogic 2Gb/sec FC card, we logged onto the appliance and found we had two new local drives to play with. With the Iometer configured for two workers, 64Kb transfer requests and 100% read operations, we saw it return a truly dismal 24MB/sec for the iSCSI target and 29MB/sec for FC in separate tests. Performance for the virtual tape drive was also well down, as a backup using ARCserve returned only 9.2MB/sec. Fortunately, the virtual tapes come into their own for restoration tasks. We selected a single file known to be near the end of the test backup and ARCserve restored it in under two seconds. Restoring the same file from a physical LTO-2 tape drive attached locally took 1min 53secs.

Tandberg Data's BAKStor appliance is a direct competitor and, although it doesn't support FC connectivity, our tests show clearly what overall iSCSI performance you should be expecting. Using the same client system and tests, the BAKstor returned 76MB/sec for a standard iSCSI disk target and a speedy 26.4MB/sec while backing up to a virtual LTO-2 tape drive. As is always our policy in the Labs when we have concerns over performance, the vendor was advised of our results. Overland Storage wouldn't confirm or deny them, but did state that it's extremely unlikely that the REO 4000 is capable of delivering the speeds we've generally been seeing in the Labs for other iSCSI and FC devices.

It's a great shame about the performance, as otherwise the REO 4000 has a lot going for it as a backup and recovery appliance. iSCSI virtual disk, tape and library plus FC support makes it highly versatile. But if you feel the need for speed then you must look elsewhere.