I wouldn't look so much at the disk configuration but at the backup method if you want frequent backups.
We have servers with around 2TB of user data, and these are snapshot and backed up twice an hour in around 10 minutes per pass, but this isn't because of our RAID 10 SAS Disks or even RAID 10 SSD database disks, it's because we have an R1Soft backup server and that performs backups at the block level and not at the file level.
We find R1Soft great as it integrates with our DirectAdmin and cPanel servers and allows customers to perform their own restores, which saves us time and offers our customers value.
We've used other methods in the past, but found they were quite resource heavy on the servers, whereas R1Soft CDP seems to be very resource light.
If it is within your budget Go for Hardware RAID 10 with BBU
__________________ Inventive Hosting UK & USA Based Servers - Trading Since 2004 Shared Web Hosting - CloudLinux
Fully Managed KVM VPS Packages and Fully Managed Dedicated Servers
UK Based24/7/365 Support - 30 Day Money Back Guarantee