Re: [Condor-users] Can VM borrow RAM from other VMs in the same computer?

[Juli Céspedes i Capdevila <juli.cespedes@xxxxxxx>]

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Hi Steffen

Thanks for your comments. They seem to fit with the observed behaviour,
and explain a few of other "weird" effects.

Steffen Grunewald wrote:
| Not only that: if a job has to be evicted for some reason, and has gained
| a larger footprint than what a single slot advertizes, it will never
| restart (because there's no matching slot machine classad anymore).
|

That explains other strange situations we experimented some time ago.

|> But if just one of the VMs jane is busy performing the jobs, they
|> complete after one day or less.
|
| You may modify your START expression, closing the remaining slots if
there's
| a large job running. Note that this will not fix the footprint issue.

I'll evaluate this carefully. (I tend to be conservative when modifying
our macros and expressions, as the cluster is heavily used here!)

| It is possible to enforce memory usage limits (which is not what you're
| looking for!); in any other regard, the jobs are on their own once they
| are started (they _are_ being watched over by their shadow/starter
though),
| and can compete for Unix resources like any other process...
|
| IMHO, with multi-core machines becoming more and more common, Condor needs
| more flexible classads (but I've heard rumours that such features are
being
| worked on and may show up very soon).
| There was a discussion about similar things before, and at least one user
| came up with "duplicated" resources (resulting in e.g. two slots, sharing
| the real resources, and another slot offering the full set of resources as
| well. START expression used to "close down" conflicting slots, depending
| on the already taken resources).

I'll have to re-read the documentation for the most recent
releases/updates. We are running a 6.8.3 cluster, since we saw no real
need to change the setup, but now I'll have to reconsider that.

Sincerely Yours,

- --
~      Juli Céspedes i Capdevila
~              IT Dept.
ICFO-The Institute of Photonic Sciences
~    Mediterranean Technology Park
~        Av Canal Olimpic s/n
08860 Castelldefels (Barcelona), Spain
~        T: (+34) 93 553 4102
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