On 02/09/13 16:32, Bill Broadley wrote: > On 02/09/2013 01:22 PM, Vincent Diepeveen wrote: >> SATA is very bad protocol for SSD's. >> >> SSD's allows perfectly parallel stores and writes, SATA doesn't. >> So SATA really limits the SSD's true performance. > > SSDs and controllers often support NCQ which allows multiple outstanding > requests. Not sure if that fits the definition of "perfectly parallel", > but it does allow for outstanding requests to be answered in the order > of the devices choosing.
Very true, and more importantly, there are multiple internal SATA controllers, making this a parallel setup once the requests make their way "into" the SSD. I agree on the premise that SATA is less than ideal for NVM memory in general, but I'm afraid I won't go so far as to say SSDs are "perfectly parallel" devices. These things have many dies within a package, but with limited buses to get at each die. Similarly, their are many packages along each channel, but with limited channels to get at each package. This all boils down to contention on the channels/buses for requests and brings to light just how important it is to choose things that aren't busy at this time. Perfectly parallel would be if every die (really, every wordline) had it's own bus. Now, that would be fast :D, and horribly expensive. Best, ellis _______________________________________________ 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
