Stratus doubles up on the ftServer 4300

It's true: Two is definitely better than one, at least when you're talking about high availability. For most server manufacturers, that means two or more identical servers in some form of cluster. Outside the clustering code, these servers are singular entities without a direct relationship with one another.

Stratus takes a different approach with its ftServer W Series 4300: It combines two discrete servers within a common backplane, operating as complete mirrors of each other. Using custom drivers, all tasks handled by the ftServer 4300 are executed in parallel. Each instruction is simultaneously computed on processors across both units. Each I/O call is handled in parallel, simultaneously. The Stratus code is essentially a traffic cop of sorts, making sure that traffic is flowing, even if there's an accident. Should a CPU or DIMM fail, the OS never sees the event and continues as normal.

Thus, the ftServer 4300 isn't really a cluster but a wholly redundant single server. In essence, Stratus has crafted a shim, abstracting the hardware layer from the OS, presenting the OS with only what it needs to see, regardless of the physical hardware in use. Suffice it to say, the ftServer 4300 is like no other server you've seen.

Two by four

Considering the spec is similar to a 1U dual-CPU server, this box is relatively large, consuming 4U in the rack version. Each server chassis in my evaluation unit came complete with dual single-core 3.2GHz 1MB cache Xeon CPUs, 2GB DDR2 RAM, three 72GB SATA drives, and a CD-ROM drive. Each chassis has a single power supply that's housed within the chassis, as well as two gigabit NICs.

These chassis units slide into a common backplane that is little more than a shell with shared video and USB ports on the back. When the ftServer 4300 is up and running, only the equivalent of one chassis is actually available to the OS, similar to a RAID1 disk mirror.

Speaking of operating systems, Stratus currently supports Windows Server 2003 and the company's own Linux distribution. However, Stratus expects to support Red Hat Enterprise Linux 4 early this year. An OS installation on a Stratus fault-tolerant server isn't exactly like a standard install, as Stratus' suite of custom drivers need to be present. Because those custom drivers are required for all expansion cards, only Stratus-approved expansion cards, such as Fibre Channel HBAs, can be used in the server.

After racking the chassis cage, I slid each chassis in and ran power, USB KVM, and network cabling to the back. After power was applied to both units, the top CPU chassis' power button turned green. Flipping open the protective cover, I hit the button and both chassis sprang to life. A few minutes later, the Windows Server 2003 log-on screen appeared.

I ran a few benchmarks on the server running normally, and all signs pointed to it performing exactly as I would expect from a dual single-core 3.2GHz Xeon server. The disk I/O performance was slightly lower, perhaps, and this is likely due to the cross-chassis mirroring configuration that Stratus uses to maintain block-level synchronization across all disks.