From time to time we get asked things like this: I want to use a 100TiB volume with DRBD, is that supported”? The biggest public device size with DRBD known to LINBIT is currently ~600TiB. (JUNE 2019 UPDATE)
DRBD tries to ensure data integrity across different computers, and it’s quite good at it. But, as per the old saying Trust, But Verify[1. attributed either to Lenin or Kennedy] it might be a good idea to periodically test whether the nodes really have identical data, similar to the checks that are[1. or at least […]
The sync-rate controller is used for controlling the used bandwidth during resynchronization (not normal replication); it runs in the SyncTarget state, ie. on the (inconsistent) receiver side.
The TL;DR version: don’t use data-integrity-alg in a production setup.
There is quite a bit of confusion about the DRBD configuration value al-extents (activity log extents), so here’s another shot at explaining it.
Similar to the recent post about setting the vm.min_free_kbytes value there’s another sysctl that might improve the behaviour: the dirty ratio.