* as long as the *entire* cluster is not upgraded, live migrations
will fail with a strange error message, for example:
Could not pre-migrate instance static-gitlab-shim.torproject.org: Failed to accept instance: Failed to start instance static-gitlab-shim.torproject.org: exited with exit code 1 (qemu-system-x86_64: -enable-kvm: unsupported machine type
Use -machine help to list supported machines
)
note that you can generally migrate *to* the *newer* nodes, just
not back to the old ones.
a workaround for this issue is to use `failover` instead of
`migrate`, which involves a shutdown. another workaround might be
to upgrade qemu to backports.
*`gnt-cluster verify` might warn about incompatible DRBD
versions. if it's a minor version, it shouldn't matter and the
warning can be ignored.
### upgrade discussion
On the other hand, the [upgrade instructions](https://sources.debian.org/src/ganeti/3.0.1-2/UPGRADE/) seem pretty confident
