Wednesday, January 22, 2014

When to use Flux and When to use XSEDE

This is a cross post from my post at the main HPC day job.  For details on Flux visit the Advanced Research Computing website.  For the topic of the post below be sure to read How Flux Works.

We had a user ask the following:
I am a bit confused about what the XSEDE program is. On your website, you
indicate that XSEDE provides computing at no cost to researchers. Who is
eligible to use the XSEDE computing at no charge? What is the incentive for
using the for-fee Flux service if XSEDE is free?
I had never thought of this case before and it is very important.  I have copied our reply to the user below for anyone else who has had this question before. Text in [square brackets] added for clarity in this post.

I should start by pointing out that I [Brock Palen] am both a CAEN-HPC employee/Flux/Nyx Admin as well as the XSEDE Campus Champion for campus.

XSEDE has no monetary cost, but does have an resource application process where you propose the use for the requested resources.  Flux has no matching policy, if you can bill a shortcode [University Account] you can get Flux Time generally.

XSEDE is provided by the NSF and is open to any open research in the country that passes their allocation review process.

Beyond the allocation policies for access, the provisioning of resources once you have access is different.

A Flux allocation is much more like a lease.  Within our resource definition we generally promise that if you have 32 cores, you can run 32 cores _now_.

Xsede works as a debit card that is oversubscribed.  You have X hours you can burn up, and within each resources policies your job will run if you have enough hours left AND the resources are idle. Thus jobs may/will queue on Xsede.

So Flux gives you much more 'right now' access and might be a better platform for development.  Xsede will let you have bigger jobs, but they will take time before they start and turn around to job start will/may be longer.

Lastly if you use any commercial software the license may not allow you to run it on Xsede.  We have many such packages on Flux and it is easier for us to make software license restrictions locally on Flux. No such restrictions are possible on Xsede generally.

There are other pros and cons.  Personally I would try to use them both.  Flux resources can be provisioned quickly (normally same or next work day)  large Xsede requests are only checked 4x/year other than startup and classroom allocations  which are much more often (2 weeks on average).

Additional thoughts: There are many different resources available to researchers.  I would encourage you to contact us early in your planning process to discuss all the options available.

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