[Gluster-users] IOPS and CPU cycles, what is the relationship between the two?

[Oliver Schad]

On Mon, 08 Sep 2014 02:03:47 +0300
Eliezer Croitoru <eliezer at ngtech.co.il> wrote:

> The question is a fundamental for understanding storage and not 100% 
> about GlusterFS but I fell like it's the right place to ask it.
> 
> I am trying to understand CPU cycles vs IOPS.
> Per each IO There must be a number of cycles of the CPU.

It's not that much:
https://en.wikipedia.org/wiki/Direct_memory_access

> So in order to choose the right CPU couple factors are needed to be 
> right for the task.
> For example a standard 7.2k RPS disk have maximum IOPS throughput.
> A SSD drive will have twice and more IOPS throughput.

Usually at least more than factor 50, usual SATA disk with ~ 150 IOPS,
SSDs starting with ~ 7.500 IOPS (until 70k IOPS also in consumer disks
and above 100k IOPS in server equipment).

> How can I calculate the maximum IOPS per CPU\machine possible?

Take a look at the main board and the CPU where the connections between
IO (disk, network) and CPU are. They all have a specific bandwith.

Additionally you have max IOPS on your local discs, max IOPS on your
storage controller. You have to find the bottle neck yourselfs.

> There sure to be taken in account the Network traffic IOPS and also
> the whole network handling code using up cycles etc.

Handling the protocol layer may fill a CPU but TCP-Offloading exists to
make that better. What you want to do is to learn system
engineering. ;-)

Best Regards
Oli
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