[Samba] CTDB load

Orlando Richards orlando.richards at ed.ac.uk
Wed Oct 8 01:54:11 MDT 2014

On 08/10/14 04:41, Amitay Isaacs wrote:
> On Tue, Oct 7, 2014 at 2:48 AM, Orlando Richards
> <orlando.richards at ed.ac.uk <mailto:orlando.richards at ed.ac.uk>> wrote:
>     Anyone fancy commenting on measuring load on ctdb?
> What exactly are you trying to do?  Since CTDB is single threaded you
> can check the CPU usage of ctdbd and consider that as the load on CTDB.

Hi Amitay,

thanks for the response. I'm trying to get a measure of how much our 
ctdb is doing - so that I can then get an indication of how much it's 
capable of on different nodes. We're suffering from cluster stability 
issues just now, and the statistics tool is giving us data to look at 
which we're hoping will be informative.

>     If I do 'ctdb statistics', I get a bunch of numbers back. The one
>     I've picked on to look at as a general indicator of load is
>     "total_calls". This is incrementing at the rate of 3,000 - 10,000
>     per second on my cluster nodes. Any thoughts on the relevance of
>     that number as a general load metric, and what you'd expect to
>     "normally" see the rate that that number increases by in ctdb?
> Various ctdb statistics are just statistics.  They will give you a
> summary of amount of work CTDB has done since it started or since the
> last statistics reset.
> total_calls or client --> req_calls is the count of number of record
> requests ctdbd received from samba (smbd/winbindd).  On a busy cluster,
> you would expect lots of record requests sent to ctdbd from samba.  It's
> possible to measure the rate of requests processed per second and may be
> considered as load on ctdb.

What's your experience with the kind of numbers you'd expect to see here 
in various "normal" environments? Is 10,000 calls per second "crazy 
high", "just normal", or "quite low"?

        Dr Orlando Richards
Research Facilities (ECDF) Systems Leader
        Information Services
    IT Infrastructure Division
        Tel: 0131 650 4994
      skype: orlando.richards

The University of Edinburgh is a charitable body, registered in 
Scotland, with registration number SC005336.

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