Only slightly off topic, Back when mainframes roamed the earth, I was a systems programmer on IBM VM systems for an oil company.
One of the performance and tuning trivia that went around went something like this (my memory is probably wrong, but you can get the idea. Assume 1 cpu cycle takes one second. That means running from cache long running instructions take 1 to 5 seconds. Getting a line from memory would take 5 to 10 seconds (new memory to put in cache after writing the old cache to memory if needed) Writing/reading a page to a drum or head per track disk was equivalent to 5 to 10 minutes. A standard disk drive, well that is 30 to 45 minutes. And to access tape, lets talk days to weeks. ... It would be nice if someone could update this allegory to modern machines, and include some SAN and/or NAS type access times, especially since we don't 'do tape' much anymore. Tape technology in those days was 2400' 1/2" wide reels at 6250 bpi and .25" breaks between blocks written. (I obviously spent way to much time using it if I still remember that!) In my last several years working I did TSM Backup and disaster recovery, so speeds and feeds were important then too. This being 'retired' is ok, but I still miss the work, but not the stresses. It took me 6mo to figure out how much stress I had been under for so many years. ... Jack - the 'Fred Flintstone' of computers PS: <war story warning> In college I ran on an old computer, a CDC 1600 I think, it had 8 7track 256BPI tape drives. No disk. The OS was on one tape, it paged on 2 more, typically 1 or 2 were 'scratch tapes' and the rest were for 'user program use'. It ran FORTRAN IV well, but the one COBOL compile I did on it took FOREVER! (hours for a simple program). Tape drives, key-slinger console typewriter, and line printer were all IBM branded. ... It was a gift from the US Navy to my college's Chemistry Dept, and we fixed the logic by replacing geranium based transistors that were 2 flip-flops per circuit board (about 2.5x2.5" each). 48bit words, and most instructions were 'half word' instructions, with 64K words of memory. ... Glad I didn't have to do anything but use it! A fun piece of boat anchor to see on the raised floor! I was told it cost $6,500,000 new in the early '60s. </war story warning> _______________________________________________ Tech mailing list Tech@lists.lopsa.org https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
