Backup/Time Machine solution for an office full of iMacs?

EDIT: For anyone coming across this question, the best solution I've found is a cloud backup company called Backblaze — it's in the cloud, so no longer have to worry about hardware failures and we now just have a large network drive for shared resources (which actually is also then backed up via Backblaze)!.

Original question:

In our office we have ~8+ or so iMacs. Currently we're backing up to individual hard-drives via TimeMachine.

We're looking at creating a more stable backup solution, one that is kept away from the iMacs in the networking room, so all backups are centralised.

I was thinking of using something like a Drobo with plenty of HDD space, that all of the iMacs back up to.

However, ideally, I don't want people to be able to see the backups of other machines.

Is it possible to have a centralised backup HDD that is write only, in conjunction with Apple Time Machine?

Or any other solution that may be relevant, ideally from someone else who already has an office of Apple machines and backing them up in a clever way.

Install a copy of the OS X Server app on a spare Mac with a pile of storage connected to it. Create a share for each Mac that you need to back up, and connect each Mac to its own share. That way, each Mac only sees its own backups. You can also limit the size allowed for each share if you like.

Another advantage of having an OS X server on the network is that it can serve as a cache for downloaded updates from Apple, so each update will be downloaded only once, and stored on the cache.

There are other services that are available, and all you need is a spare Mac (I use a Mac Mini) to act as server, and a copy of the Server app from the App Store for $19.99 or so.

You can simply put an Apple Time Capsule in your network and select this as Time Machine backup volume. And you may choose an encrypted backup to ensure more privacy. This works perfect in my office with a dozen MacBooks.

A more cost efficient solution may be a 3rd party solution like a Synology DiskStation containing a Raid 1or 5. Synology also offers Time Machine support which works seamless for me at home.

You can backup multiple Mac's to a central Time Capsule. On each Mac: System Preferences > Time Machine > Select Disk. Choose the same Time Capsule for all your computers. Each computer will have a separate .sparsebundle on the Time Capsule disk.

When setting up the Time Capsule disk you can set individual accounts which should solve the security issue: Airport Utility > Choose Time Capsule > Edit > Disks > Enable File Sharing > select with accounts instead of with device password.

I assume you can use a Drobo attached to a Time Capsule (or perhaps directly) and recreate all of the above but I have never done it.