No performance benefit from enabling csums-alg

[Tim Westbrook]

We are testing to see if enabling csums-alg would reduce resync times when we have to clear metadata or invalidate a node

I have a Primary (P) and two secondaries (S1, S2)

S2 is disabled (off) to simplify interactions. 

When do any of the following I see no appreciable difference in the time between Connecting state and Consistent between 
systems with `csums-alg md5​ ` and one without that setting. [1]


* invalidate S1 on S1
* down drbd on S1 , clear metadata on S1, start drbd on S1
* disconnect network, create 1G file of 0s on P, reconnect network
* disconnect network, create 1G file of random on P, reconnect network 

This is on version 9.2.4 of the driver

Just trying to understand this feature better,.


Thanks,
Tim


[1]
  // with
  net {
    after-sb-1pri discard-secondary;
    verify-alg md5;
    csums-alg md5;
  }
  // without
  net {
    after-sb-1pri discard-secondary;
    verify-alg md5;
  }

  note -verify works so I assume the md5 ability is in the kernel