We're backing up our SAN using disk-based backups, with two rotating sets of eight 4TB drives in RAID5 mode. This has worked for us well over the past 3 years, I just upgraded to larger drives and moved from a slow NAS to a fast DAS.
The weak link has always been the software (Retrospect). Its instability, useless email reporting, and lack of support for rotating sets made it a very annoying compromise. My candidate for replacement has been Archiware P5 (PresStore), but now I'm wondering... what am I really gaining this way? I've used Chronosync for smaller tasks and really like it... but can I trust it to handle all of our data?
For backing up w/ PresStore:
A "real", hefty program that you can trust your company's storage to
Spending $1,500 on it makes you feel like it's a serious solution...
Is PresStore's encryption more reliable than FileVault2?
For synchronizing w/Chronosync:
Designed to be used with disks, while PresStore has a complete tape library-based paradigm that I still find confusing for disk sets.
Leverages the advantage of disks that all data is instantly accessible; in case of a catastrophic failure we can even mount the backup as "online" storage without needing new storage to restore it to.
Data is natively stored, you're not dependent on the software for restores.
I've never had issues with Chronosync, including running test backups of our entire SAN. It takes about 20 minutes to scan 14TB and a million files, and then copies/verifies at the speed of the storage.
This program may have the best software support I've ever experienced. The developers even helped me with custom patches for our (now-defunct) Avid Unity 4.
Online > Nearline ( Disk to Disk -server-1 Raid1 to Raid2) Chronosync
Online > Backup (Disk to Disk server-1 Raid1 to server-2 Raid1 ) Chronosync
Backup> Backup (Disk to LTO server-2 Raid1 to LTO5) PresStore