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Overview of StashCache

The OSG operates the StashCache data federation, which provides organizations with a method to distribute their data in a scalable manner to thousands of jobs without needing to pre-stage data at each site. The StashCache data federation is best suited for per-job data set sizes between 1 and 50 GB, with no more than 1 TB for a complete workflow.

Organizations export their data from an origin server, and the data is streamed to jobs from a set of cache servers distributed throughout the OSG and Internet2. Jobs can achieve lower latency and higher throughput for data transfer by using a nearby cache instead of accessing the origin directly.

The map below shows the location of the current caches in the StashCache federation:

StashCache Map

Architecture

The StashCache federation consists of three service types:

  • Origin: Keeps the authoritative copy of an organization's data. Each origin is operated by the organization that wants to distribute its data within the StashCache federation.
  • Cache: Transfers data to clients such as jobs or users. A set of caches are operated across the OSG for the benefit of nearby sites; in addition, each site may run its own cache in order to reduce the amount of data transferred over the WAN.
  • Redirector: Tells a cache service which origin to download data from. The redirectors are run centrally by OSG Operations.

The structure of the federation is illustrated below:

StashCache Diagram

A job will request data from a cache. The cache will serve the requested data from local disk if possible. Otherwise, it will query a redirector for the origin server that provides the data, download the data from that origin server, and then serve the data to the job. A copy of the data will be kept on the cache for use by future jobs.

Joining and Using StashCache

This material is based upon work supported by the National Science Foundation under Grant Nos. 1148698 and 1836650 . Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.