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BDS: A centralized near-optimal overlay network for inter-datacenter data replication Zhang et al., EuroSys’18
(If you don’t have ACM Digital Library access, the paper can be accessed either by following the link above directly from The Morning Paper blog site).
This is the story of how inter-datacenter multicast transfers at Baidu were sped-up by a factor of 3-5x. That’s a big deal!
For large-scale online service providers, such as Google, Facebook, and Baidu, an important data communication pattern is inter-DC multicast of bulk data — replicating massive amounts of data (e.g., user logs, web search indexes, photo sharing, blog posts) from one DC to multiple DCs in geo-distributed locations.
To set the scene, the authors study inter-DC traffic at Baidu over a period of seven days. Nearly all inter-DC traffic is multicast (91.1%), highlighting the importance of optimising the multicast use case.

When looking at the individual transfers, there is great diversity in the source and destination DCs. Thus it’s not going to suffice to pre-configure a few select routes: “we need a system to automatically route and schedule any given inter-DC multicast transfers.”
60% of the transferred files are over 1TB Continue reading