[DRBD-user] Summarizing DRBD memory usage

[Iustin Pop]

There have been lately some very good threads about DRBD memory usage.
I'd like to ask if, after this, my understanding about the total memory
usage is correct.

If I understand correctly, we have:
  - per-TB 32MB of memory used, statically, independent of over how many
    DRBD minors it is spread
  - a per-minor usage of up to:
    - sndbuf-size for the TCP connection (can be ignored)
    - PAGE_SIZE * max_buffers
    - probably some other small values (kernel structures or such) which
      can be ignored for normal cases

This means, a 1TB device with the defaults of sndbuf-size 132KB and
max_buffers 2048 will use (at max, e.g. during resync):
  - 32MB for bitmap
  - 132KB for TCP connection
  - 8MB for the buffers

I.e. this is ~40MB.

On the other hand, a 1TB device split over 8 x 128MB, will have 32MB +
8x8MB =~ 96MB.

Is this correct?

thank you!
iustin