Infrascale is a great backup solution that provides both the software and storage under one roof at some of the cheapest rates in the business. You buy data in pools and separate them out to the computers as you want. All this is done under software that you completely white label. So your client doesn't know it is all being done under infrascale.
It is the cheapest way to truly protect data. Backs up clients data. You can customize the schedule and methods, Create real snap shots for your important data, Have real effective ransomware protection, all managed under one place and one white labeled piece of software that is easy to use for any MSP.
More expensive as B2 with CloudBerry, but really can't think of anything else.
I have been using the SOS service to backup all of my data and it's been very simple to set up & to use.
SOS is really the best out there - super secure too.