[Sheepdog] Databases, write barriers etc

[Brian Candler]

I am considering using a Sheepdog-based KVM cluster to run a Postgres
database, where data consistency is important.

Are there any problems or issues I should consider in this application? Does
Sheepdog support write barriers?  Should I use ext4 with journal
checksumming?

I notice the design doc says "The write request is successful only when all
replicas can be successfully updated", so I guess fsync shouldn't return
until all data has been written. But I'd be grateful for any real-world
experiences with databases on KVM+Sheepdog.

Thanks,

Brian.