TOPIC:

Could you please elaborate a bit on choosing DRBD version 8.3.15.
Would upgrading the included DRBD components to the 8.4 release branch be of advantage?
Do you know about any drawbacks with other/newer versions of DRBD and standard XenServer components (kernel, OVS, ...)?

In our testing, DRBD 8.4 was not stable with a XenServer standard dom0 deployment. Major network related issues were encountered. 8.3.15 has been extremely stable. Based on this, we would not recommend trying newer DRBD versions for now.

We expect that the next major XenServer release will no longer require DRBD to be installed as the newer kernel should have it included already.

Stating major network issues with XS standard dom0 deployments, you are referring to the default Open vSwitch network backend, right?
Do you have test cases with 'old' Linux bridge mode also?
'Creedence' will apparently fix quite a few things.

We dont have any test cases pre open-vswitch. The specific issue we encountered with DRBD 8.4 was that the replication network became completely unresponsive during DRBD initial sync. Also, I seem to recall /proc/drbd was not updating either during a sync.

Soon we will begin testing/development against the next major XenServer release - AKA Creedence Alpha. So far this is based on linux kernel 3.10 which should include DRBD 8.4.3 out of the box. We are anticipating that only the DRBD userland tools will be needed during installation when we get there.

Thank you for the heads-up! Do this mentioned issues still prove to be true with the latest XenServer kernel and OVS hotfixes? XenServer 6.2 with XS62ESP1005 in our case.

We have not done any testing with DRBD 8.4 against the latest XenServer releases and will likely not since we are planning to start work against XenServer Creedence soon.

You are welcome to give it a try and report back your findings. If it does work, some additional development may be required in the event that the userland DRBD admin tools differ between 8.3 and 8.4