Posts

Trust, but verify

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 can be] done for RAID sets. Read more

DRBD and the sync rate controller (8.3.9 and above)

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. Read more

DRBD causes too much CPU-load

The TL;DR version: don’t use data-integrity-alg in a production setup. Read more

“al-extents” explained

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. Read more

Make the kernel start write-out earlier

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. Read more