CCL: W:hardware for computational chemistry calculations

 Sent to CCL by: benne278 []
 On 30 Sep 2005, Perry E. Metzger wrote:
 >In my comment, I'm referring to the more general case
 I know.  That is why I called hyperthreading a "special case".  There
 also some drawbacks to hyperthreading but they are not particularly
 relevant to this thread.
 > So, the question becomes, does the difference in speed for your app
 > between having enough memory to hold the whole scratch file in buffer
 > cache increase speed sufficiently to justify the marginal $1000
 > cost? That depends on how I/O bound you are.
 I'm not trying to provide a full decision tree here.  In fact, I'm
 deliberately trying to avoid that because it will lead to another tedious
 thread, and the original poster didn't provide enough information anyway.
 If the OP's quantum calculations use 30 GB of scratch, that will likely
 change the answer vs. if they are only using 2 GB of scatch.
 The simple question was if SCSI ever has an advantage, and the simple
 answer is that yes, sometimes it does, even if it isn't often.  Therefore,
 it should be considered, even if you ultimately end up deciding the money
 is better spent on something else.
 If I might make a suggestion for people who post performance questions to
 the list, it might help if they offered up short (~ 60 min?) test jobs.
 I bet there are a few people on the list who would be willing to run a
 short example job on their hardware for you, and this will give you an
 answer that is probably a lot more helpful than somebody listing all the
 many variables that interact to determine performance.  You might even find
 out that changing the code you are using would be a bigger boost than
 buying faster hardware.