Re: high throughput storage server?

[Zdenek Kaspar <zkaspar82@gmail.com>]

Dne 24.2.2011 21:43, Matt Garman napsal(a):
> On Tue, Feb 15, 2011 at 7:03 AM, Roberto Spadim <roberto@spadim.com.br> 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.
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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.