So, I’m now happily using Greyhole. Good for me, you say?

Not long ago, a 1 TB hard drive that was part of my storage pool died (my fault really, handling it while it was powered up). Greyhole handled this beautifully, re-creating duplicate copies of the files that were stored on that drive to continue protecting all my data. But I didn’t have enough free space on the other drives to allow all the duplicates I want to be created.

Perfect timing to test a very nice feature of Greyhole: inclusion of remote hard drives in the storage pool.

I have a 1 TB hard drive attached to my Airport Extreme router, that I use as my Time Machine backup destination (the Airport makes it available through AFP and Samba). It had about 600 GB free. Perfect candidate for this.
I simply mounted that drive on my file server, and included it in my Greyhole storage pool. I then launched “greyhole –balance” to force Greyhole to balance the available space evenly on all drives. Files transferred at about 5MB/s from my file server to the remote drive, so I had to wait a couple of hours for the 600GB to get filled.

I now have about 10-12 GB free on all the drives included in my storage pool, and all my files are correctly protected once more.

Further thinking revealed an interesting use of such remote hard drive in a Greyhole storage pool. Since remote access is much slower than local access, it wouldn’t make much sense to keep a remote drive in my pool forever, since I do care about performance. But, for some files, performance is not an issue. For example, for my Photos share, I keep a copy of each file on all available drives in my storage pool (I do care about those files!) A remote drive could be used to store a copy of those files, and nothing else. The trick to achieve this is to simply indicate a very high number as the minimum free space for that drive in the Greyhole configuration.
With such a configuration, the remote drive will only be used as a last resort choice when Greyhole chooses where a file copy should be kept. And, minimum free space will be ignored in the case of files that needs to go on all drives.
What this means is that the remote drive will be used to store a copy of the files in my Photos share, and it will be used to store file copies on other shares only if all other hard drives are filled to capacity. Which is nice.
My important files are now backed up remotely (well, in the next room is remote to the file server!), plus if all my fast drives get filled, this slower option will be used until I can free up some space (by adding another internal drive, most likely).

How cool is that? Very cool I think. I don’t know any other pooling / redundancy system that would allow you to do something like that with such ease! :)
I’m glad to be using Greyhole right now. And you? :D