[Drbd-dev] User's Guide fix for variable-rate sync; missing doc in man pages

[Andrea Spadaccini]

Hi Florian,

[…]

Thanks for the quick fix!

> Andrea, regarding your other comment about disk-options: that one _is_
> documented, in the drbdsetup man page.

Thanks for the pointer. I think it should also be mentioned in the
drbdadm man page.

Cheers,
Andrea