Re: [Condor-users] Looking for something like CpuBusy for Disk

[Lans Carstensen <Lans.Carstensen@xxxxxxxxxxxxxx>]

Ian Chesal wrote:
> On Fri, Sep 3, 2010 at 2:30 PM, Lans Carstensen 
> <Lans.Carstensen@xxxxxxxxxxxxxx <mailto:Lans.Carstensen@xxxxxxxxxxxxxx>> 
> wrote:
>
>     The seriously cool way would be to standardize a global resource
>     classad type and allow for expression logic to have a way to
>     directly address all resource ads that are deemed to apply to a
>     particular slot and job.
>
>
> That certainly takes it a step further. To that end: a way to put *any* 
> type of ad in to the collector would really be interesting. So you could 
> collect and reference anything you want and use it during matchmaking 
> and execution decisions.
>
> Baby steps though. :) I don't want to dream my way out this being possible.

Agreed.

>     This reminds me that the other way we address the common use case
>     for this class of problem is with concurrency limits on jobs - but
>     that doesn't handle slot-level use cases, only job-level ones.
>
>     Partitionable slot-level resource/concurrency limits would be a
>     useful addition towards that goal.  Then you might want to apply
>     some feedback mechanism to make the upper bound of that
>     partitionable slot dynamic based upon some business logic (like a
>     global resource classad).
>
>
> Ahh...it's fun to dream. In all honesty though, while it's a bit 
> cumbersome to setup once, Startd cron jobs can handle a lot of what 
> we're dreaming about here when it comes to slot-level concurrency 
> controls. And once you get one set up, the rest follow pretty easily.

True, startd cron's can (and have) been used to do all sorts of things - 
but I haven't seen one applied to do host-level concurrency limits 
(successfully).  The "cron"/timeperiod nature makes doing resource 
counters unsafe for resource reservation.  Do you have an example of one 
of those, or is it (like I currently believe) a gap in functionality 
that you end up having to build up custom slot types around to handle?

For instance, say I have a SAN-attached host and want to enable no more 
than 3 concurrent SAN IO jobs while also enabling other job types. 
Today I'd have to set up a special partitionable slot with a SAN 
attribute and start expression to only allow SAN jobs and do something 
like dedicating 3 CPU's and some amount of RAM towards that 
partitionable slot.  Or make 3 SAN slots with dedicated memory 
resources.  And then add a partitionable slot for all remaining CPU, 
memory, and local disk resourcse.  There's no way to apply a "SAN" 
resource counter, and no way to alter the number "3" live based on 
actual SAN link utilization or storage subsystem latency.  Right?

If you have a startd cron for that class of use case, we'd be interested 
in seeing it.  Other competing resource schedulers have host-based 
resource counters for this reason.

-- Lans Carstensen