On 30 December 2014 at 14:28, Christian Balzer <[email protected]> wrote:

> Use a good monitoring tool like atop to watch how busy things are.
>
> And do that while running a normal rados bench like this from a client
> node:
> rados -p rbd bench 60 write -t 32
>
> And again like this:
> rados -p rbd bench 60 write -t 32 -b 4096
>
> In particular (but not only), compare the CPU usage during those runs.

Interesting results -

First 14 seconds:
CPU : 1 core at sys/user 2%/1%, rest idle
    HD :  45% Busy
SDDD: 35% Busy

- After 14 seconds
CPU : 1 core at sys/user 20%/7%, rest idle
  HD : 100% Busy
SDD: 30% - 50% Busy

Journal size is 10GB
max sync interval = 46.5
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