I'd like to build an NAS that has 2 Western Digital Red 3TBs (with a Gigabit connection to a combined wireless / Gigabit router), simply to provide real-time continuous backup of a PC (with a Gigibit connection to the network) and a laptop (with an 802.11n network connection). The 2nd drive needs to be hot-swappable, so that I can swap it out for use as an off-site backup as required, and the NAS should then automatically create a new 2nd copy when a replacement drive is installed. (I would prefer not to use RAID0, but instead simply have each of the 2 continuous backups operating independently.)

Would it be feasible to build a PC that has these features? If so, any suggestions for motherboard. processor, case and backup software would be appreciated.

For a multiple drive setup i would probably build it my self, as raid cards, cpu and a lot of other things matter. But you case seems simple, specially for the 2 hdd nas. If your hobby is building pcs, and you enjoy it, the go for it, but my advise is just get a prebuild and call it, depnding on your budget and transfer needs maybe something like

Synology DiskStation 2-Bay (Diskless) Network Attached Storage DS213
Synology DiskStation 2-Bay (Diskless) Network Attached Storage DS213+

Thank you for the response.

I'm not desperate to build one myself, but my understanding is that prebuilt NASs are rarely very quiet. A self-build using the latest components should achieve quieter solution that is also more energy-efficient.

What are you going to use to provide "real time" backup?

What you want to do is pretty easy if you don't need true real time backups. A batch script setup in Task Scheduler would do what you need. Have it check for the presence of the second drive and if it exists do a sync with robocopy. Have it run every few hours or however often you feel comfortable with.

I'm aware that Acronis TrueImage (for example) has a "Nonstop Backup" feature, but this needs to be manually maintained (to delete old data). So I'm hoping for something a little more sophisticated, but I'm new to NAS technology and products, and am open to suggestions.

I've been reasonably happy with Crashplan for a set it and forget it type backup. You can configure it to backup as often as every 15 min. It is a bit of a memory hog and you need to be able to run it on both your PC and the NAS, so many pre-built ones may not support it. The other thing is that it is only a data backup, it doesn't to a system level image.

If you build it there is a big chance it can be lowered to where its inaudible, but at the same time if this is your intention, then i would go a case like antec solo II that has suspension for 2x 3.5 hdds, but this will also make them not hot swapable, so something will have to give.

Personally i still think Synology is a good bet for your situation, i had a DS111 and personally i didnt feel it was too noisy, and the stations are so small that you can place them almost anywhere, you only need a network conection and power, then it can be placed anywhere. Now my experience was decent not saying silent but i also didnt have it on my desk, was below a rack where abient noise was higher. Some of the later models have started using 120mm fans (mine was like 60mm if i remeber correctly, but mine is also a 1 disk so not much space for a fan, 2x hdd sometimes use 80mm)

Good luck with your choice,

I appreciate your taking the time to share your experience, and I'll give your advice very careful consideration.

I wasn't aware of Crashplan. I've now looked at their site, and it is clearly a very flexible option. Thank you for the suggestion.

Using any type of file system "sync" or disk imaging for real-time backup would make absolutely no sense. It's effectively the same as trying to use RAID for backup, and every bit as bad. Accidentally delete a file? Oops... it's immediately deleted from your "backup".

True backups account for state _changes_. Accidentally delete a file? If you have a true backup, then you can restore the file from the backup. How often you can backup is limited by how much space you have for storing the backups and the speed of running the backup operation.

I too wouldn't consider using synching software for continuous backup, but you seem to be unaware that continuous backup solutions are far more sophisticated than simple file synching. Take a look at the functionality that TrueImage and Oops!Backup offer.

a bit ot and fwiw, windows 8 now has "file history" that supposedly works like apples "time machine".

http://lifehacker.com/5958865/how-to-us ... or-windows

Check out BackupPC. It's a bit of a config to get setup initially, but once setup with rsync clients, it will back up anything, does great disk sharing, easy web interface for clients, runs automatically, e-mails reports, etc.

It's what I'm using on my home built NAS.

http://backuppc.sourceforge.net/

BackupPC cannot deal with open files, which is a pretty big fail for a backup system.