International Data Corporation (IDC) has issued its annual high-availability (HA) server marketplace survey by category for 1997 through 2003. IDC projects that the HA server market grew 30.2 percent in 1999 and will reach 35.5 percent growth in 2003. According to the report, this market segment is heating up and will grow from $63.3 billion in 1999 to $85.2 billion in 2003. The report cites improved technology and the ever-increasing demands that a variety of applications—including Internet, scientific computing, and transaction systems—make on servers and OSs as the reasons for this unusual growth in a relatively stagnant market. IDC defines four different availability levels (ALs) in server systems: • AL4 is transparent to the user, and involves no interruption of work, no transactions lost, and no degradation in performance; the system provides 100 percent component and functional redundancy. • In AL3, the user remains online, the current transaction might need restarting, and the user might experience performance degradation; automatic failover transfers user sessions and workload to backup components and multiple system connections to disks. • AL2 interrupts the user (who can log back on), and the user might have to rerun some transactions from the journal file and might experience performance degradation; the system transfers user work to backup components and multiple system access to disks. • In AL1, work stops, an uncontrolled shutdown occurs, but the system maintains data integrity; the system uses disk mirroring or RAID and a log-based or journal file system for identification and recovery on incomplete and in-process transactions (an incomplete transaction might require reentry). Using the AL definitions, IDC claims that AL1 offers 99.9 percent—three nines—uptime; AL2 offers four nines uptime; and AL3 offers five nines. At 99.999 percent uptime, your server is down only about 5 minutes a year. AL4 servers will failover in a way that the user won't notice. Geoffrey Dutton, the IDC analyst reporting these results, finds that UNIX is still the most popular OS for servers; IDC expects this preference to continue. The firm projects that Windows 2000 and Windows NT's share of the overall server market will increase significantly, from 14 percent of revenues in 1999 to 27 percent in 2003. Win2K and NT have a small percentage of today's HA systems with few vendors selling fault-tolerant NT systems. Few vendors offer AL2, AL3, or AL4 systems using 32-bit Intel architecture. Among those vendors' products are Sequent's NUMA Center (from two clusters to 64 nodes) and the upcoming Stratus ftServer series. Stratus will make five nines available for an entry point of $30,000. IDC concludes "the server market exhibits high price elasticity, and HA Windows servers at attractive price points will be able to tap into pent-up demand." IDC has published some of these results in a survey entitled "Fault-Tolerant Computing for the NT Masses: Did Stratus Get There First?" (IDC report 21729).