On Fri, 2013-04-19 at 06:51 +0200, Shawn Heisey wrote: > Using SSDs for storage can speed things up dramatically and may reduce > the total memory requirement to some degree,
We have been using SSDs for several years in our servers. It is our clear experience that "to some degree" should be replaced with "very much" in the above. Our current SSD-equipped servers each holds a total of 127GB of index data spread ever 3 instances. The machines each have 16GB of RAM, of which about 7GB are left for disk cache. "We" are the State and University Library, Denmark and our search engine is the primary (and arguably only) way to locate resources for our users. The average raw search time is 32ms for non-faceted queries and 616ms for heavy faceted (which is much too slow. Dang! I thought I fixed that). > but even an SSD is slower than RAM. The transfer speed of RAM is faster, > and from what I understand, the latency is at least an order of > magnitude quicker - nanoseconds vs microseconds. True, but you might as well argue that everyone should go for the fastest CPU possible, as it will be, well, faster than the slower ones. The question is almost never to get the fastest possible, but to get a good price/performance tradeoff. I would argue that SSDs fit that bill very well for a great deal of the "My search is too slow"-threads that are spun on this mailing list. Especially for larger indexes. Regards, Toke Eskildsen
