[DRBD-user] can not open /dev/drbd0: No such device or address

[Graham, Simon]

I can see at least one problem with your config:

  on app4 { 
      device    /dev/drbd0; 
      disk      /dev/hda5; 
      address   10.0.0.2:7788; 
      meta-disk internal; 
  } 
  on app5 { 
    device     /dev/drbd0; 
    disk       /dev/hda5; 
    address    10.0.0.2:7788; 
    meta-disk  internal; 
   } 

You have the same IP address defined for both nodes (app4 and app5 are the nodes where the drbd replicas run - you have to configure the actual IP address used to communicate with these in the address setting).

Simon