Dne 24.2.2011 21:43, Matt Garman napsal(a): > On Tue, Feb 15, 2011 at 7:03 AM, Roberto Spadim <roberto@xxxxxxxxxxxxx> wrote: >> disks are good for sequencial access >> for non-sequencial ssd are better (the sequencial access rate for a >> ssd is the same for a non sequencial access rate) > > I have a more general question: say I have an ultra simple NAS system, > with exactly one disk, and an infinitely fast network connection. > Now, with exactly one client, I should be able to do a sequential read > that is exactly the speed of that single drive in the NAS box (assume > network protocol overhead is negligible to keep it simple). > > What happens if there are exactly two clients simultaneously > requesting different large files? From the client's perspective, this > is a sequential read, but from the drive's perspective, it's obviously > not. > > And likewise, what if there are three clients, or four clients, ..., > all requesting different but large files simultaneously? > > How does one calculate the drive's throughput in these cases? And, > clearly, there are two throughputs, one from the clients' > perspectives, and one from the drive's perspective. > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html For rough estimate, try to simulate your workload in small scale, ie: create files on your disk (fs), and run multiple processes (dd) reading them. To summarize things together watch loads, ie for disk(s): iostat -mx 1. HTH, Z. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
