hmm... 4TB of images?
sounds like she is a very hardworking and pro photographer
i'm also working in IT industry, taking care of a couple of hundreds TB of data. (note: i use the word <data> instead of <information>; because how useful are those, i dunno..) ahaha
coming back to the topic, having that amount of huge data will equates to a higher amount of budget/$$ to handle them..
...unless, she is willing to be a little more hardworking too in performing backups. There are simple cloning tools out there that some H/W vendors calls "OTB". Personally used one of the better ones for my personal home networked PCs which houses 2.5TB of mixed stuffs.
it is capable of cloning/imaging my HDs and "span" them into several image files which you can use several 500GB HDDs to keep it. So, whenever that S/W says, "insert a blank/new HDD", you just change the USB2 enclosure till it says, "complete".
however, this does not seems to provide a satisfactory solution/alternative to her problem.
Try this other slightly costs more alternative:-
(1) i had recently got a cheap NAS + VTL solution from one of the major storage vendor in the market to handle 06TB of FTP data only. What separates this vendor from the other major storage vendors is that it is capable of "de-duplication" and "virtual tape library".
How to use?
- it is just a black box with lots of 500GB HDDs RAID5 + 01 HotSpare together
- With 04TB of useable space, you can choose to use it for either/both methods (NAS and/or VTL)
- if you use it as a NAS, it provides approximately 04TB of backup storage
- if you use it as a VTL, it provides approximately 28TB of virtual tape storage (H/W compression)
- if you use both, it depends on usage %
(2) Use a free S/W tool called "FreeNAS" in a old PC housed full of SATA/IDE drives together in your networked-PCs and turn on the backup S/W's scheduler (use the OS built-in/any backup S/W backup application) to perform the automated backup/clonings unto that old PC with FreeNAS.