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Chris LuandGitHub
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A multi-disk volume server keeps one .ecx / .ecj / .vif set per volume on a single disk while ec.balance scatters the shards across the others. Every EC operation on such a node crosses that split: startup registration, balancing the sidecar disk's shards away, rebooting in that state, and mounting a shard delivered to a disk that has no local sidecars. Each of those transitions is handled by a different mechanism (per-disk scan, cross-disk reconcile, mount-time .ecx lookup), individually tested but never as the sequence a production node actually lives through — where the output state of one transition is the input of the next. A regression in any hop shows up as shards that exist on disk while the master's view says otherwise, and every topology-driven repair then works against the wrong shard set. The layout, volume id and collection mirror a support case. The second test pins the failure floor when the sidecar disk itself dies: shards on the surviving disks may drop out of the registered view, since nothing can read them without the .ecx, but their files must survive so restoring the sidecars restores the volume.