The only NAS that Apple officially supports for TM backup is the TC. Some people use a NAS...sometimes they stop working, and finally some NAS boxes work better than others. Synology has a good reputation...
FreeNAS works flawlessly. Apple has no enterprise class solution for backups. They only offer a home or VERY small business solution. Nothing for the company who owns dozens (or hundreds) of Macs.
As said above, Synology works and Drobo works well too.
But watch it. What if the Synology or the Drobo chassis or main board dies? The data may still be OK but you'd have to wait for the box to be repaired. So there is good reason to own TWO of these things. Having only one is not good if you ned the data from a dead box TODAY.
Or you can use a NAS that is built from standard PC hardware and standard software. FreeNAS works but is kind of overkill for a small home user with only a couple Macs. As it needs to have 3 to 6 drives installed to be economical.
Whatever you do do NOT go cheap. If you needs a small just buy an Airport router and add an external USB disk. Plug the USB drive direct to the Mac to do the first backup, it will be MUCH faster then way, then move the drive to the Airport. But if all your data does not get on one drive yu are going to need an array. FreeNAS using ZFS is the most robust product out there.
----------
How do you know that you have never had corruptions?
Do you perform routine file integrity checks so you know for a fact that nothing is corrupted?
Have you ever had to perform a bare-metal recovery?
Yes. I've tested this. First off, I run a job on the NAS to checksum the entire disk array periodically. It actually reads every sector on every drive and verifies CRCs.
Then as a test I pull the power cable off one of the disks while it is writing data and verify that the system still operates with a failed drive.
I would never suggest using a NASf or disk array without doing the above. You really need both. Especially the periodic CRS verification. Otherwise you might have bad data on a failed block and never detect it.
One More Thing, always use incremental backups so you never overwrite data known to be good. Time Machine gets this right and will fill up the entire drive before it resorts to overwriting
Also keep the data in more then one location, rotate to an off site or use a cloud based device. Don't depend on just one backup.
The other feature that is nice to have on a NAS is remote replication. It does this: You Macs write to the NAS then periodically your NAS connects up to it's twin and "syncs" so that the twin has a copy of the data. Lcate the twin as far away as you can, in sme other city is best but at least in a different room.
Need to thinkabout (1) house fire, (2) theft of the equipment, (3) lightening hitting the power pole and taking out everything that is plugged into an AC outlet.
lastly TEST your backup system, try to do a restore, verify that faults are detected and so on.
FreeNAS does all of the above. An has enough performance to use multiple Gigabit Ethernet cables or a 10GB port if you can afford it. But do you have this much data?
