Tuesday, January 17, 2012

Bulletproof Backups with the ReadyNAS Duo (Update)

I thought I'd do an update to one of my most popular blog posts: Bulletproof Backups with the ReadyNAS Duo:

I've had my ReadyNAS Duo nearly four years now, and have experimented with all sorts of things and reached some conclusions:


I struggled for a couple years with versioned backups. Because you have quite a lot of disk space, you can get away with making multiple, complete copies of your data for daily and weekly backups. In fact, using the built-in ReadyNAS software it's the best you can do.

But if you've got thousands of files and most of them don't change often, this feels very wasteful. A while ago I discovered the rsnapshot add-on. rsnapshot only copies files that have changed, and creates hard links for those that haven't. So suddenly you can have many days/weeks worth of versioned backups in very little disk space. Awesome!


Hard Links Are Evil

A warning about hard links. If your ReadyNAS ever decides it needs to check the disk (fsck), all those thousands of rsnapshot hard links will bring it to its knees. This has only happened to me once, thankfully!

Your options in this case seem to be either: kill fsck, delete all your rsnaphot backups (and hence the hard links) and run fsck again. Or wait out the mysterious blue pulsing light:

Mysterious Blue Pulsing Light

Sometimes the ReadyNAS just sits there ominously with a blue pulsing power light. You can't connect to it during these times. Worse, this mystery state can last for hours! If you're like me you installed RAIDar once when you first bought your ReadyNAS, and then forgot all about it. However RAIDar is very useful for telling you what your NAS is doing during these pulsing light times, and stopping you resetting it in impatience.

Root That Sucker

I resisted the EnableRootSSH and ToggleSSH add-ons for years, because if you use them and subsequently mess something up, you probably can't ask for support. But if you're careful they can be very useful.

For example, when configuring rsnapshot, I found it necessary to manually edit /etc/cron.d/rsnapshot and set it to:

0 9,18 * * * root /c/addons-config/rsnapshot/hourly.sh
0 14 * * * root /c/addons-config/rsnapshot/daily.sh
0 16 * * 1 root /c/addons-config/rsnapshot/weekly.sh

This is because by default rsnapshot runs at midnight, but I have my ReadyNAS configured to power down overnight.

Bringing The Horse To Water

Although there's lots of rsnapshot goodness once your data is on the ReadyNAS, actually getting it there can be troublesome. I went through a lot of different backup programs. Some of them are truly awful. I won't name and shame them, but here are some problems to watch out for:
  • do they have a special driver that syncs the data? These frequently BSOD'ed my PC
  • do they mess up the folder case when they sync, especially if you have two folders with different case at different places in your heirarchy (e.g. C:\foo\Finances versus C:\foo\bar\finances)
  • do they have catalogs/indexes/other mechanisms that make them horribly slow to copy thousands of files
  • can they do file filtering based on wildcard matching
  • can they exclude folders based on wildcard matching, especially nested folders (e.g. *\tmp\)
The absolute best I found was SyncBackSE. It does it all, and does it fast, and does it without any nasty surprises!

Teaching The Horse To Drink

Even with a great product like SyncBackSE, you still need to take care how you schedule your backups. If you've got thousands of files, even if they don't change often, your backup software still has to scan over them every time.

I settled on configuring half a dozen backup jobs. Critical files were scanned more often (say, hourly) but in small groups (say, just My Documents). Less critical files were scanned less often (say, daily) in larger groups (say, C:\Program Files).

Exactly What It Says On The Tin

The ReadyNAS is a great Network Attached Storage device (e.g. hard drives in a box), but it's pretty lousy for anything else. It's really underpowered if you try to use it as a server, or load it up with too many add-ons or streaming services. If that's what you're after, you really need more than 256MB RAM and a slow CPU. Apparently the Duo v2 is faster, but it's still only 256MB RAM.

Your Mileage May Vary

Some things I got right the first time:
  • it's definitely too slow to use as an 'active' drive that you run programs off.
  • keeping all paths relative to some distant drive letter (like N:) is handy for restores.
  • despite some misgivings, I've had no problems at all powering down the ReadyNAS and swapping drive trays as a way to take off-site backups. However, remember that the drives are EXT3 formatted. This makes them a pain to try and read in Windows, and the ReadyNAS doesn't do NTFS. So it can still take a while to restore all that data into a usable form.
But all in all, the ReadyNAS Duo is a complete win!


Anonymous said...

You can bump the ReadyNAS Duo's RAM up to 1GB. It uses a standard module. The ReadyNAD forums have a lot on this.