Hi René, everybody!
René Fournier wrote: > [[...]] However, even if the Index can't fit in memory (4GB of RAM, lots > free), just reading it from disk should allow sub-millisecond response, no? No chance! Of course, performance of disk drives varies, but AFAIK typical values are in the range of 7 - 10 ms per random access. Assuming the (very unlikely) optimum case of one index access and one data access, this would put you into the range of 15 - 20 ms just for fetching the stuff from disk, not including any CPU time to traverse the data structures etc. Just do some math: A disk with 7,200 rpm has 120 revolutions per second, so it needs a bit more than 8 milliseconds per revolution. Random access means you have to wait (on average) for half a revolution (4 ms) until the desired block passes the disk head, and before that the head needs to be positioned at the proper cylinder (the drive's data sheet might give that time). I guess that even with SSD you will not reach sub-millisecond response times if the data is not in RAM. > > Strange thing is that I've used my laptop for benchmarking for the past five > years and it's always produced results fairly typical or at least consistent > in relation to our servers. This new thing is... new. IMO, the most influential factor in single-user database benchmarks are - disk performance - RAM size for caches, cache replacement - history, cache preloading Their relative importance will vary, depending especially on data size. As long as your data size is small enough that RAM differences between server and laptop don't matter too much, performance on the laptop may be a good prediction of that on the server. With multi-user benchmarks, CPU performance, number of cores etc becomes another important factor, again the relative weights will vary. Regards, Jörg -- Joerg Bruehe, MySQL Build Team, joerg.bru...@sun.com Sun Microsystems GmbH, Komturstraße 18a, D-12099 Berlin Geschaeftsfuehrer: Thomas Schroeder, Wolfgang Engels, Wolf Frenkel Vorsitzender des Aufsichtsrates: Martin Haering Muenchen: HRB161028 -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
