At 10:34 PM 10/16/98 -0700, Alan Hannan wrote:
For total system uptime 90.0% (one nine or less) Desktop systems. 99.0% (two nines) Intermediate business systems 99.9% (three nines) Most business data systems and workgroup servers 99.99% (four nines) High-end business systems and your friendly neighborhood telco 99.999% (five nines) Bank Data Centers and Telco Data Centers, some ISPs 99.9999% (six nines) Only God and Norad live here. 99.99999% (seven nines) Even God doesn't have pockets this deep.
What's your source for this data?
You mean, besides 22 years in the system design and development trade? Well, you can start with the various companies I have worked for. Then the manufacturing specs on the various systems. My last analysis involved two-headed server setup on HP 9000 series T520 with MC service guard and shared RAID5. HP guarantees that at three nines. With the right add-ons I got it to four nines (Complete second site in AZ, 1500 miles away). Very expensive. Five nines would have broken the budget, that was Wells Fargo. Northrup/Grumman MD-18 flight-line support. The PacBell broadband system was quad redundant data centers in Fairfield and San Diego. I was hired in as the Techinical Architect for that system. Again, HP equipment. That system would have hit five nines, or better, in production. I think we were pushing past $16M on that system, thirty-six specially configured T520's plus RAID packs. Various systems I worked on in Patrice Carrol's org in MCI COS (Garden of the Gods facility), including the Fraud Management System. This stuff is more art than science, too many non-deterministic variables. Experience is the only thing that counts. It tells you which formulaii to use and when they have a chance of working. I should have my web-site up again this week-end, we're converting to FastTrack with LiveWire, in addition to Apache-SSL/mod_perl. ___________________________________________________ Roeland M.J. Meyer, ISOC (InterNIC RM993) e-mail: <mailto:rmeyer@mhsc.com>rmeyer@mhsc.com Internet phone: hawk.mhsc.com Personal web pages: <http://www.mhsc.com/~rmeyer>www.mhsc.com/~rmeyer Company web-site: <http://www.mhsc.com/>www.mhsc.com/ ___________________________________________ I bet the human brain is a kludge. -- Marvin Minsky