Product Reviews

It may have suffered from being marketed as the poor man's alternative to fibre channel, but iSCSI (Internet SCSI) is starting to look like a serious, albeit somewhat slower, alternative for network storage. We've seen a number of good-quality SME appliances appearing on the market, such as Adaptec's Storage Array iSA1500. But the mighty Super-i-Stor T4000 from Boston takes iSCSI firmly into the enterprise, and at a price that fibre channel can't hope to compete with.

The system is based around a pair of 12U rack cabinets, while storage is handled by a quartet of Supermicro storage servers running Wasabi's Linux-based Storage Builder software. This provides iSCSI target services and web-management facilities. Physically, the servers are up to the usual solid standard we expect from Supermicro, and each is equipped with a good specification based around a single 2.4GHz Xeon processor and 1GB of memory. The cabinets support up to 15 hard disks and each came supplied with a dozen 250GB SATA/150 drives in hot-swap carriers, giving a total 12TB of raw storage. Boston also advised us that 400GB SATA drives will be available by the time you read this, allowing the T4000 to deliver an incredible 24TB of storage.

The drives are all managed by a 12-port 3ware controller providing hardware RAID support. Adaptec would be the only candidate if all 16 drive bays are to be supported, as this is the only manufacturer currently offering a 16-port controller (see issue 120, p186). Furthermore, although cable-related clutter has been kept to a minimum in this configuration, the 3ware Multilane card (see p198) would be a tidier alternative. A minor complaint is that the Toshiba IDE flash memory card and controller have been left loose underneath the central cooling fan array, and should be secured.

A feature of this system is RAID options that are almost limitless, and it's possible to come up with completely new and unheard of configurations using a combination of the local hardware and software options plus OS-managed arrays on servers running the iSCSI initiator. For example, the first storage server was configured with four, triple-disk RAID5 arrays controlled by the 3ware card. Wasabi's Storage Builder supports software-managed arrays and the four RAID5 groups were then configured as

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a single RAID0, giving a total 1.7TB of fault-tolerant storage. Doing this with all four cabinets would allow us to log on to four RAID50 arrays and then from the OS we could create, say, another striped array in software with all four logical drives giving us a RAID500 array. Along with the four storage servers, the system came supplied with a basic Supermicro 1U server, which can run either Linux or Windows Storage Server 2003 and is designed to function as a gateway by amalgamating all the iSCSI storage and presenting it to the network. A simple 3Com 16-port gigabit Ethernet switch looks after the network connectivity, while a Fujitsu KVM switch and monitor provide local access to all components.

Configuration won't take long, as the Wasabi software provides a tidy remote web-management interface for each cabinet. From here you can view the status of all components, configure network parameters and view a detailed system log. Management access can be controlled by username and password and iSCSI CHAP authentication selected if required. Target devices are easy enough to create and assign to either of the two gigabit interfaces, and Jumbo frames are also supported. Volume groups are used to carve up available storage. The menu shows a tree with the 3ware controller at the root, with physical and logical drives displayed above. Striping and mirroring are supported but, at the time of the review, the Wasabi software was in beta and the mirroring option had been removed temporarily.

For performance testing we used four Windows Server 2003 systems configured with Microsoft's iSCSI initiator version 1.05. With one system logged onto a single cabinet we saw the open-source Iometer utility report an average data throughput of 89MB/sec for one disk worker, ten outstanding I/Os and 64KB transfer requests - similar to that delivered by Adaptec's iSA1500. With four servers logged on to each cabinet we saw a good cumulative throughput of 328MB/sec.

Curiously, we found general processor utilisation to be well above the expected average when using software initiators. On a dual Xeon server, for example, we found utilisation to be in the region of 50 per cent when testing the Adaptec iSCSI appliance. With the server logged on to the Wasabi target, we saw this rise to more than 70 per cent. However, as the software is still in beta phase we expect this to be resolved soon.

There's no denying the Super-i-Stor T4000 shows clearly what iSCSI has to offer at the enterprise level of the storage market. It combines a huge capacity with masses of RAID options and fault-tolerance and, although as yet unfinished, Wasabi's Storage Builder target software delivers a smart web-management interface and plenty of features. Furthermore, although fibre channel will always have the upper hand for performance, it can't compete at this price point in terms of storage capacity.