[ovirt-users] Seamless SAN HA failovers with oVirt?

[Chris Adams]

Once upon a time, Juan Pablo <pablo.localhost at gmail.com> said:
> Chris, if you have active-active with multipath: you upgrade one system,
> reboot it, check it came active again, then upgrade the other.

Yes, but that's still not how a TrueNAS (and most other low- to
mid-range SANs) works, so is not relevant.  The TrueNAS only has a
single active node talking to the hard drives at a time, because having
two nodes talking to the same storage at the same time is a hard problem
to solve (typically requires custom hardware with active cache coherency
and such).

You can (and should) use multipath between servers and a TrueNAS, and
that protects against NIC, cable, and switch failures, but does not help
with a controller failure/reboot/upgrade.  Multipath is also used to
provide better bandwidth sharing between links than ethernet LAGs.

-- 
Chris Adams <cma at cmadams.net>