Sorry, forgot to change the subject on my first posting. I was reading a comment this morning about something Microsoft had published to the effect that there were vendors guaranteeing 99.9% uptime for NT. The guy who wrote the reply did the math for what that means, and the results are very interesting. Quote below: OK, now what does a 99.9% uptime guarantee mean? Well, it means that at bottom, a guarantee that the machine will not be down for more than one one-thousandth of the time. If we assume that we have a stable system, ie., one where the system is not taken down for software upgrades, etc., then we are looking at the time from a system crash (strictly, I think, from the time that the crash is actually noticed) to the time that the system is running again. So, below is a little table that shows the best guaranteed up-times for various values of the above restart time, rounded up. Restart time Uptime 10 mins 7 days 30 mins 21 days 120 mins 84 days etc ..... The conclusion I draw is that either (a) NT crashes very often and is quick to restart or (b) NT crashes less often but takes a long time to restart.. Considering I've had Netware servers and UNIX boxes that stayed up for 6 months at a time, maybe we need to re-think what constitutes acceptable availability. "99.9%" sounds great, but if you look at it this way, it's really pretty abysmal. Anyone care to do the math for their mainframe systems for comparison?
On 1999-10-15 22:46:22 +1000, Hall, Ken (ECSS) wrote:> I was reading a comment this morning about something Microsoft had > published to the effect that there were vendors guaranteeing 99.9% > uptime for NT. The guy who wrote the reply did the math for what that > means, and the results are very interesting. > > Quote below: > >> OK, now what does a 99.9% uptime guarantee mean? Well, it means >> that at bottom, a guarantee that the machine will not be down for >> more than one one-thousandth of the time. If we assume that we have >> a stable system, ie., one where the system is not taken down for >> software upgrades, etc.,I think this is a big assumption. Apart from the occasional crash in the evening which wasn't noticed until next morning, all our long downtimes in the last few years were caused by software or hardware upgrades (and with the large HP-UX servers, were are generally in the 99.9% range). Basically, I think a guarantuee of 99.9% uptime is a guarantuee that you won't have to upgrade/reinstall more than once per year. You will also have to consider that users generelly aren't interested in a running OS but in some service. So if I have to shut down samba for half an hour to enlarge some file system, that's half an hour of down time as far as my users are concerned. hp -- _ | Peter J. Holzer | Nobody should ever have to be |_|_) | Sysadmin WSR / Obmann LUGA | ashamed if they have a secret love | | | hjp@wsr.ac.at | for writing computer programs that __/ | http://wsrx.wsr.ac.at/~hjp/ | actually work. -- Donald E. Knuth -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 371 bytes Desc: not available Url : http://lists.samba.org/archive/samba/attachments/19991015/63569992/attachment.bin