Our environment:
Three sites:
Site A: 3 hosts, 25 VMs, ~6T of data
Site B: 3 hosts, 15 VMs, ~1.4T
Site C: 8 hosts, 117 VMs, ~7.5T
T3 between sites, Cisco WAAS devices (WAN accelerators).
OSes - Mostly Windows, about 15 linux boxes.
Based on a 6 VM test (3 linux, 3 windows), 2 of which do not yet have change block tracking, I am getting about 100MB/s backup speeds using a single 64bit Windows VM, 4 CPU, 4G Ram, as the backup server in VBA mode. CPU utilization is about 60%, using about 2G of RAM.
Goals:
* 1 day RTO and RPO
* Offsite the data, daily or weekly
* Dedupe to save on disk space
* Inexpensive backup disk storage (currently using an OpenSolaris box serving NFS to ESX hosts).
* Retention:
Daily for 31 days
Weekly for 8 weeks
Monthly for 13 months
Yearly for 3 years
My questions:
1. What is the best configuration of backup servers?
I am thinking one for sites A and B, and two for site C (or maybe just two parallel jobs?). Doing the math tells me a single appliance, single job, would backup site C in about 13 hours. We use Equallogic arrays, and since I cannot figure out how to do a read-only mode on the volumes, I will probably stick with using VBA mode, not SAN mode.
2. What is the best way to get the data offsite? Should I backup across the WAN (site A's VBA backing up site B, etc., possibly with a local linux box to do the synthetic processing), or use the backend storage to replicate the finished backup set, using rsync or similar?
3. How do I guarantee Linux backups? Windows has VSS, but for Linux, it looks like crash consistent backups only?
4. Any difference backing up to an NFS mount, or backing up to a vmdk image on NFS? I know, I should test this…
5. What is the best retention setup? I am thinking of three jobs. Dailies for 56 days to cover weekly and daily backups in a single job. Then separate jobs for the monthly and yearly backups, and I would either script those or just manually kick them off.
6. What class of backend storage do I need? Currently my OpenSolaris box as a target is pretty fast, but it is really just a dev box. Can I get away with an inexpensive NAS like a QNAP, Synology, Iomega, etc?
Thanks for help with any of the above, I really appreciate it!

Best,
Scott