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Site Planning

The OSG vision is to integrate computing across different resource types and business models to allow campus IT to offer a maximally flexible high throughput computing (HTC) environment for their researchers.

This document is for System Administrators and aims to provide an overview of the different options to consider when planning to share resources via the OSG.

After reading, you should be able to understand what software or services you want to provide to support your researchers

Note

This document covers the most common options. OSG is a diverse infrastructure: depending on what groups you want to support, you may need to install additional services. Coordinate with your local researchers.

OSG Site Services

The OSG Software stack tries to provide a uniform computing and storage fabric across many independently-managed computing and storage resources. These individual services will be accessed by virtual organizations (VOs), which will delegate the resources to scientists, researchers, and students.

Sharing is a fundamental principle for the OSG: your site is encouraged to support as many OSG-registered VOs as local conditions allow. Autonomy is another principle: you are not required to support any VOs you do not want. As the administrator, your task is to make your existing computing and storage resources available to and reliable for your supported VOs.

We break this down into three tasks:

There are multiple approaches for each item, depending on the VOs you support, and time you have to invest in the OSG.

Note

An essential concept in the OSG is the "pilot job". The pilot, which arrives at your batch system, is sent by the VO to get a resource allocation. However, it does not contain any research payload. Once started, it will connect back to a resource pool and pull down individuals' research "payload jobs". Hence, we do not think about submitting "jobs" to sites but rather "resource requests".

Pilot Jobs

Traditionally, an OSG Compute Element (CE) provides remote access for VOs to submit pilot jobs to your local batch system. However, today, there are two options for accepting pilot jobs at your site:

  • Hosted CE: OSG will run and operate the CE services; the site only needs to provide a SSH pubkey-based authentication access to the central OSG host. OSG will interface with the VO and submit pilots directly to your batch system via SSH. By far, this is the simplest option: however, it is less-scalable and the site delegates many of the scheduling decisions to the OSG. Contact help@opensciencegrid.org for more information on the hosted CE.
  • OSG CE: The traditional option where the site installs and operates a HTCondor-based CE on a dedicated host. This provides the best scalability and flexibility, but may require an ongoing time investment from the site. The OSG CE install and operation is covered in this documentation page.

Runtime environment

The OSG requires a very minimal runtime environment that can be deployed via tarball, RPM, or through a global filesystem on your cluster's worker nodes.

We believe that all research applications should be portable and self-contained, with no OS dependencies. This provides access to the most resources and minimizes the presence at sites. However, this ideal is often difficult to achieve in practice. For sites that want to support a uniform runtime environment, we provide a global filesystem called CVMFS that VOs can use to distribute their own software dependencies.

Finally, many researchers use applications that require a specific OS environment - not just individual dependencies - that is distributed as a container. OSG supports the use of the Singularity container runtime with Docker-based image distribution.

Data Services

Whether accessed through CVMFS or command-line software like curl, the majority of software is moved via HTTP in cache-friendly patterns. All sites are highly encouraged to use an HTTP proxy to reduce the load on the WAN from the cluster.

Depending on the VOs you want to support, additional data services may be necessary:

  • Some VOs elect to stream their larger input data from offsite using OSG's "StashCache" service. This requires no services to be run by the site
  • The largest sites will additionally run large-scale data services such as a "storage element". This is often required for sites that want to support more complex organizations such as ATLAS or CMS.

Site Policies

Sites are encouraged to clearly specify and communicate their local policies regarding resource access. One common mechanism to do this is post them on a web page and make this page part of your site registration. Written policies help external entities understand what your site wants to accomplish with the OSG -- and are often internally clarifying.

In line of our principle of sharing, we encourage you to allow virtual organizations registered with the OSG "opportunistic use" of your resources. You may need to preempt those jobs when higher priority jobs come around. The end-users using the OSG generally prefer having access to your site subject to preemption over having no access at all.