>> In any event, your original statement used to be wholly correct. >> It has >> changed to a certain degree to "SSDs are about IOPs," which isn't >> quite the same thing. However, more pointedly, with modern HDDs >> barely approaching 200MB/s and SSD solutions approaching 2-4GB/s, >> this is an increasingly limited viewpoint. We have to start >> considering their use for bandwidth. > > Find me an application that needs big bandwidth and doesn't need > massive storage. > > > > Digital waveform recording and playback.. e.g. in radar simulators. > You need very wide bandwidth, but not a huge amount of storage (e.g. > If I'm playing back a synthetic response to a 1 millisecond pulse with > 2 GHz BW, I only need 10s of Megasamples at most, but you need 10 > Gsample/second sorts of bandwidth) > > One might thing, heck, just slap a few GByte of RAM in there and be > done with it, but if you're simulating a radar with 10 different pulse > types, and you have 10-20 simulated targets each with several > different viewing aspects, you pretty quickly need a "library" of > several thousand pulses/returns to choose from.
Yeah well i remember negotiating about writing CUDA code for simulation software of something similar. Don't think that this example applies. You want it in RAM for a proper simulation :) --- Nope... you want to store it in disk.. a) 4 bytes/sample @ 20 Megasamples/pulse is 80 Mbyte/pulse b) * 1000 pulses is 80 GB. That's a lot of RAM (and a lot of power, if you DID buy that much ram). A few Gbyte/second coming out of a SSD makes it actually feasible to "stream from disk array" and keep that 1-2 GSample/Second pipeline full. And on the receive side, where you want to capture the transmitted pulses (or returns), a similar sort of thing applies, although SSDs aren't a ball o'fire for write speed, they ARE faster than spinning magnetic media, so to get a given throughput, it takes fewer drives. Sometimes, it's the "number of drives" that is the cost determining aspect. You don't need a lot of space, but you do need a very fast transfer rate, and ganging up drives in parallel is how it's done. The instantaneous seek aspect of a SSD is also nice, because you don't have to worry about rotational latency in this kind of application. _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
