Bulletproof Backups with the ReadyNAS Duo

Update: I wrote up my findings, four years on, in this new blog post!

I just invested in a ReadyNAS Duo, which is a mean-looking little device:

It's small (smaller than a shoebox), quiet (about as loud as a fridge), got terabytes of storage and can run autonomously doing all kinds of things (FTPing files, hosting web sites, downloading BitTorrents, etc.).

It's so flexible infact, there seems to be a lot of confusion on the forums around which strategy to adopt to make best use of it. So I thought I'd write this quick blog on how I use it as a really good backup device.

Step 1: Don't Use It

Well, don't use it as your main hard disk drive (HDD) anyway. It's tempting to try and move all your important files onto it, so that if your PC dies you can just hook up a different PC and off you go. But networks are much, much slower than local HDDs and it just isn't practical. Even e-mail programs run sluggishly if you're serving their EXE over the network.

Instead, get a good mirroring program like MirrorFolder, and have it mirror your HDD to the ReadyNAS frequently (even in real-time, if you like).

Step 2: Rely on it

Expect your PC to fail. Create a separate partition on your local HDD and call it something distant from C: (like N:). Then move all your important programs to it and configure them to be running off N: drive. This can be a tedious process, but once it's done your entire environment is relative to N:, which means as (and when) your PC fails, you can hook up another PC, map drive N: to the ReadyNAS and be up and running again nearly instantly.

Of course, it'll be slow (see Step 1), so ultimately you'll want to copy everything back to the 'mirrored partition' model on that new PC, but if your old PC dies and you need to continue working immediately for, say, the rest of the day it should suffice.

Step 3: Trick the software

Oddly, the ReadyNas Duo's weak spot is its backup software. You can't do weekly backups, or monthly backups, you can't filter out file types etc. etc.

Most suggestions on the forums are to work around this using some 'real' backup software instead, but that's silly because then it ties up your PC again while doing the backup. Instead:

1. configure MirrorFolder (or equivalent) to only mirror the files you want to backup
2. configure the ReadyNAS' built-in backup software to copy everything from the mirror into the backup share (this bit doesn't involve your PC, so you can run it overnight)
3. set up different backup jobs, one for each day of the week, that backs up the mirror to different folders each day. You now have a rolling seven day backup
4. create another backup job that, on Saturday, takes Sunday's backup and copies it to yet another folder (called, say 'Last Sunday')
5. create yet another backup job that, on Friday, takes 'Last Sunday's backup and copies it to yet another folder (called, say 'Sunday Before Last'). Keep doing this so that you get monthly backups

Step 4: Trust nothing

Of course, even though your ReadyNAS is a secure backup of your PC, if you lose both at the same time you're still screwed. I'd recommend keeping the ReadyNAS in a separate part of the house to your PC, so that it's not lost in the event of a localized fire. But if the entire house burns to the ground, that's no help. Some of the forum backup strategies say 'buy another NAS' but there's a much nicer way:

The ReadyNAS Duo has 'swappable RAID', whereby you can swap one of the HDDs and the ReadyNAS will resync it. This feature is meant for when one of the HDDs is about to fail.

But you can also use it for off-site backups!

Invest in a third HDD and NAS drive tray (yes, you buy them separately if you hunt about a bit - the ones for the ReadyNAS NV+ are compatible). Then, on a weekly/monthly basis, swap one of the drives. Because you buy a third tray, you can leave the HDD screwed into the tray, so swapping takes very little time.Take the HDD you took out and keep it off-site. Now, even if your house burns down, you're covered!

Update - I've been advised there are problems with this style of swapping:

1. Apparently both the SATA connectors on the drives and the ones inside the ReadyNAS are quite fragile, and likely to break with repeated swapping.
2. If the drive is being written to as you swap it, those files might not be written correctly. Best to power the ReadyNAS down before doing the swap.

Instead, you can buy a USB enclosure for your extra HDD and backup over USB. Two things to note with this approach:

1. If your USB enclosure is anything like mine, you have to unscrew it to put the HDD in. When you do this, you get to see just how flimsy the SATA connectors are!
2. This is not a good solution if you have a serious amount of data. Re-syncing a 500GB HDD with RAID-X takes about an hour. With USB it'd take days.