It's 100% correct.
That's why ideally I'd like Exchange virtualised, because in that case I can rely on following solution stack, not touching Microsoft clustering:
- SMVI for OS / binaries backup
- SME for Exchange mailstore backup
- VMware HA for unplanned hardware failures
- VMware VMotion for planned hardware maintenance
And all that with just single Exchange licence (for mailbox role), one OS to manage & patch and one copy of data!
When we throw SnapMirror into the mix (possibly with VMware SRM), we have site-level resiliency, still maintaining a single copy of Exchange binaries - fantastic simplicity comparing to native Exchange clustering!
Regards,
Radek