Google is experimenting with remotely mounting jobs’ binaries and data packages.
Each package is served as an ext4 filesystem atop an iSCSI-mounted block device fed
through dm-multipath and dm-verity. A typical job might run on O(1K) machines,
employing a N-to-1 multipath configuration yielding O(10K) short-lived iSCSI
sessions. Google thus sees O(100K) iSCSI sessions set up and torn down every
minute, a rather atypical iSCSI deployment. We will explore the challenges
presented by this deployment at scale.