Since Stratus didn't let me keep the system around for a year (99.999% uptime means less than six minutes of downtime per year), I can't confirm the reliability figure that it promises, but if my limited testing is any indication, the ftServer is one good way to achieve that kind of uptime.
What you get
The server is actually two complete servers configured to work as one machine. The system consists of two 2U servers that are inserted into a 4U rack enclosure. Each system includes its own CPU, RAM, Ethernet interfaces, power supply, disk drives, and so forth. The enclosure provides the USB, serial ports, a modem, and VGA output for the system.
I received the system from Stratus with Red Hat Enterprise Linux Advanced Server (AS) 4 pre-installed, along with the fault-tolerant utilities. Stratus offers several configurations; I received the 4300, which included two 3.20GHz Intel Xeon CPUs, four 74GB 10K RPM SATA hard drives, two 160GB 7,200 RPM SATA drives, and two sets of two sticks of 1GB DDR2 RAM. Since everything is redundant, that breaks down to one virtual CPU, 2GB of RAM, two 74GB drives, and a 160GB drive.
Setting up the ftServer, physically, is easy -- you can have it unboxed and up and running within 10 minutes. After the units have been loaded and locked within the enclosure, powering up the master unit brings up both systems.
Once I powered the unit on, it displayed the Stratus startup screen and then the familiar Red Hat boot sequence. For the most part, you won't notice any difference between one of Stratus' ftServer systems and any other system running AS. The standard utilities are all the same, and there's no difference in the way you manage services such as Apache or Postfix on the ftServer compared to how you manage them on any other hardware.
Redundancy in action, Redundancy in action
The system performs well enough, but it seems a shame to have all that additional hardware "going to waste." Actually, it's not being wasted -- each system processes commands simultaneously, so that if a component goes out, the other one can step in and take over. With this setup, there's really no single point of failure with the system itself. It's extremely unlikely that the power supplies or CPUs or RAM would fail in both systems simultaneously.
Each 2U unit has two Ethernet interfaces. The interfaces are "bonded," meaning that the first interface on the first and second unit act as a bonded pair, and the second interface on the first and second unit also acts as a single Ethernet interface as far as the operating system is concerned. While I was running the system I tried pinging to and from the system and unplugging one interface at a time -- the system never missed a packet.
I also tried unplugging one of the units while the system was running. Again, aside from some error messages from the monitoring system, there was no evidence that anything was amiss at all. Users connecting to the system wouldn't notice a thing.
The modem I mentioned earlier is included so that the system can "phone home" if a component does go offline. Even though the system can continue to operate if a part fails in one system, that leaves the ftServer with a single point of failure, so it's imperative that a replacement part be installed as soon as possible. The folks at Stratus tell me that if the system does go offline, they'll be alerted and will then go through their contact list to connect with someone at the organization where the system is installed to notify them of the outage.
This redundancy does come at a cost. You are limited to Red Hat's enterprise offerings (or, ugh, Windows) on the ftServer. Stratus doesn't offer SUSE or other Linux distros as supported options, so if you're running a certified or homegrown Linux app, you'll need to be sure it's good on Red Hat. However, it shouldn't require any customization or tweaks to run on the ftServer.
The Stratus documentation I received with the system is an OK reference, but not a very good manual. I think the system would benefit from a shorter "getting started" guide that covers the utilities you use to monitor and control the ftStratus.
Not for everyone
I was impressed with the ftServer. It's a nifty piece of engineering, and should deliver the kind of uptime necessary for some applications. However, the system is overkill for many setups. In many cases, it would be more effective to have several separate systems in a high-availability configuration than a single ftServer.
The system I reviewed, as configured, clocks in at $30,755. According to the Stratus folks I spoke with, the entry-level systems start around $10K and larger dual-core systems can run more than $60K. They recommend Stratus systems for "applications where the consequences of downtime are costly, in terms of money or protection of life or property." If one of those situations apply to you, put Stratus on the shortlist of vendors to talk to.