This article will help you determine whether or not your WAN link is suitable for your application’s write workload. DRBD Proxy is intended to smooth out bursts in I/O, but cannot break the laws of physics.
Refer to the KB article on collecting and averaging IO statistics to determine your application’s average write workload.
The next step is to get the compression rate that DRBD Proxy is able to achieve.
- Connect DRBD over DRBD Proxy using a fast (local) network connection.
- Write some representative data to DRBD.
- Get the compression ratio from the output of
drbd-proxy-ctl show connections --human-readable. This applies to DRBD Proxy version 4, refer to instructions below for version 3.
Suppose you determine that your compression ratio is 15.83, and your calculated rate of change averaged 68.56 Mbps, then calculate the required network rate as follows: ( 68.56 Mbps / 15.83 ) = 4.33 Mbps
This means you would need to have a 4.33 Mbps link between sites to theoretically be able to keep up with the application.
DRBD Proxy Version 3 Compression Ratio # drbd-proxy-ctl -c 'show hconnections' Name Status LAN WAN Compr r0-node0-node1 Up 1.8G 122M 0.06317To calculate your ratio, ( 1 / $Compr ), so in the example from above you should have found our compression ratio like so: ( 1 / 0.06317 ) = 15.83.
Reviewed 2020-12-01 - DGT
Updated 2025-01-28 - JRC