Determine DRBD Proxy Feasibility Over Slow WAN Links

This article will help you determine whether or not your WAN link is suitable for your applications write workload. DRBD Proxy is intended to smooth out bursts in IO, but cannot break the laws of physics.

Refer to the KB article on collecting and averaging IO statistics in order to determine your applications average write workload. 

Then, get the reported compression rate (according to Proxy):

  # drbd-proxy-ctl -c 'show hconnections'
    Name             Status        LAN        WAN    Compr
    r0-node0-node1   Up            1.8G      122M   0.06317

To calculate your ratio, ( 1 / $Compr ), so in the example from above
we should have found our compression ratio like so: ( 1 / 0.06317 ) = 15.83

Round this number up (being optimistic), and use that as our ratio ( the following assumes our calculated rate of change averaged 68.56 Mbps):
    ( 68.56 Mbps / 16 ) = 4.285 Mbps

This means we would need to have a 4.285 Mbps link between sites to theoretically be able to keep up with the application. 


Reviewed 2020/12/01 - DGT