ATTO iPBridge 1550D

Fibre channel may be the network infrastructure of choice for SANs (storage area networks), but the high cost of installation and management keeps them firmly in the enterprise sector. Despite its detractors, iSCSI (internet SCSI) is proving to be an ideal SAN alternative for SMEs, as it can be implemented over standard Ethernet networks, without the need for costly fibre-channel equipment. We've brought you a wide range of iSCSI storage product reviews in Enterprise over the past 18 months, but all have been self-contained appliances providing either tape or disk storage. Companies wanting to network their own devices will find the bridge is an ideal candidate, since it can take any SCSI device and turn it into a SCSI target.

This month, we take a look at two contenders, with ATTO's iPBridge 1550D coming under the spotlight first. Although not as small as the Bridgeworks Potomac (see below), the 1550D is nevertheless a compact device. It's also well built inside and out, and ATTO has fitted a small fan inside the top cover to improve internal cooling. Installation is simple: you just connect the bridge to the network, add your SCSI devices and power up. ATTO provides its QuickNAV utility, which scans the network and automatically discovers the bridge. A handy tool when configuring multiple bridge devices is an option to remotely flash the activity LED on the selected unit. After assigning an IP address, you can use the Command Line Interface or go straight to web browser management. The latter provides easy access to configuration of Ethernet: SCSI, iSCSI and access control parameters. Devices are automatically mapped to LUNs (logical unit numbers), but you can drag and drop them for manual assignments if required. iSCSI aliases, port numbers and CHAP authentication may be modified and the CLI can be accessed, although this feature did contain a scripting bug.

For testing, we first introduced a Sony StorStation AIT260e tape drive to the 1550D, where it was identified correctly and mapped to a LUN ready for use. Along with gigabit Ethernet, we ran tests over a Fast Ethernet network to get a feel for performance where the network itself may be a limiting factor. Using Microsoft's iSCSI initiator 1.06 on a Windows XP Professional system, we had no problems logging into the bridge as a target. The system immediately identified the new tape drive, leaving us to load the relevant drivers.

Using Windows Backup, our first test over Fast Ethernet was to secure and restore a 2.5GB mix of data. We saw backup speeds of 7MB/sec, while restoring the data returned average speeds of 8.6MB/sec. Moving over to gigabit Ethernet saw backup and restore speeds improve to 10.5MB/sec and 9.5MB/sec respectively - near to native speeds for the Sony tape drive. We then replaced the tape drive with a Seagate Cheetah Ultra320 SCSI hard disk, where the open-source Iometer reported 75MB/sec raw throughput. This is near the maximum read speeds achievable for this drive and real-world tests confirmed this, as copying the 2.5GB of test data to the drive returned an average of 34MB/sec.

The 1550D is only marginally more costly than the Potomac and certainly the extra outlay is worthwhile. It offers a superior hardware specification and a more accessible management interface, while performance is noticeably better.

Author: Dave Mitchell