[sheepdog-users] symetric sheepdog cluster + quorum server

[Zoran Bošnjak]

Hello all,
I am designing a storage cluster. I am (hard) limited by 2 identical server rooms + 1 auxilary server outside of both rooms. Unfortunately, the auxilary server does not have any spare disk. It's for quorum only. 

I am considering the case of a room failure. Can sheepdog cluster still provide service in this case? This means:
- if exactly half of disk capacity is gone
- but the quorum is still OK?

It does not seem to be possible with static configuration. It requires impossible setup:
First, make sure that data write is acknowledged from both rooms. This is to be ready to degrade at any time to any room.
Second, in the case of degraded mode, forget the first rule. Apply some other replication rules for single room operation, otherwise the cluster would stall.
When room recovers, switch back to original rule (and recover data).

Can I make use of external tools (like zookeeper), to detect and react on server/room failures (reconfigure cluster to switch between modes)? Any help is appreciated.

regards,
Zoran