On 22/4/10 1:52 PM, Sander Klous wrote:
in my opinion, one of the main advantages of VMs, is it allows you to make assumptions about many things being exactly the same, on all sites. Why else would you go to the trouble?? So this:
On 22 Apr 2010, at 13:30, Sander Klous wrote:
So, I see what you mean by banned now: the policy indeed bans the possibility to impose a specific way of obtaining your workload on every site. I think that is a good thing.
is to me turning off one of the main advantages of VMs, and for a weak reason.
Okay, I will raise this point in the afternoon. As an alternative we can not ban anything in the policy related to obtaining a workload. This means that some of the images will try to connect to the batch system and we have to make sure these images are not run or won't affect the infrastructure at Nikhef. Of course this also means that these images will fail when they are started at Nikhef. If they want, other sites can do the same for images that will try to get their work from pilot job frameworks.
I'm not sure how successful this intervention will be. In previous discussions multiple sites did not like the idea of VMs prescribing the way they wanted to obtain their workload.
Just putting the policy in the background for a minute, if I would take the Alice VO as an example use case, then it doesn't make sense to connect back to the batch system when the image has been launched. A service within the VM could launch the AliEn('s have landed) pilot job framework and crunch on the data from there. In this pilot job mode, I called this the cloud-approach a while back i.e. executed on an infrastructure like Claudia i.e. close your eyes and launch a VM on some hardware (yes, I'm skipping details intentionally).
If you would use this in a batch system integrated way, then it would be launched by the batch system (INFN VM approach). This would not really mean that a pbs_mom is connecting to the site's Torque service from within the VM. If the latter would be the case, then it would act as a class 1 VM WN in the batch system of which I doubt you really want this to ever happen IMHO as it is both made off-site, has VO specific stuff added to it and would potentially mix with your regular cluster nodes.
I would change Point 7.4 "Images should not be pre-configured to obtain a workload. How the running instance of an image obtains a workload is a contextualization option left to the site at which the image is instantiated."
to:
7.4a "How a running instance of an image obtains a workload is a contextualization option left to the site at which the image is instantiated."
7.4b "The methods in which VM can be contextualized must adhere to site local policies"