Archive for NAS

Backup, RAID and Redundancy

Posted in Misc, Technology with tags , , on June 18, 2009 by evanbutson

OK so most of the people I talk to know how much of a fan of redundant arrays I am, the idea of trusting all your precious work to a single drive that can and often will fail at literally the worst time is scary. Since about 2003 I have stored all my working media on RAID arrays, first RAID 1 arrays and then when I could afford it I upgraded to a RAID 5 array, for those who don’t know a RAID 5 array allows any single drive on your array to fail and you don’t lose any data, you also only lose 1 drives worth of space as compared to half with a RAID 1 array. Now that being said I have seen RAID 5 arrays fail, sometimes for reasons other than a hard drive failing, I have had array controllers themselves go haywire and kill an array, as well as physical failures with  cabling (in my case a bad power cable) that caused three drives to fall out of an array and cause me to lose a whole bunch of my iTunes library. That’s why I don’t just rely on RAID 5 redundancy for my main server, I also have a NAS that my RAID array clones itself to each night, that way, if something terrible happens to my array (touch wood) I still have a backup that is within 24 hours of being current.

That’s all well and good but my NAS isn’t really expandable, and it is not redundant, if a drive in it fails it is toast, so I have for some time been investigating possible solution that wont break the bank. I have tested and was looking at setting up a NAS using FreeNAS, it worked, and was pretty good, but I hadn’t gone as far as rolling it out as two of my hoped for features it didn’t really support, I wanted to be able to use JBOD so that if a drive did fail I didn’t lose all my data at once, and I also wanted the drives to be able to spin down and sleep (my power bill is getting silly), well a helpful episode of Tekzilla yesterday (and also the last sadly) offered a solution, that, whilst not free fulfills all my needs and adds a few things I didn’t even know I wanted.

unRAID by LimeTech is a sollution that sort of sits squarely between RAID 5 and a JBOD NAS. Basically think of it as a JBOD where you have a series of drives (they dont have to match, and can be any size), that appear as one large pool of drive space, the data is written to the first drive in the pool first until it is full and then continues onto the next and so forth, that way if a drive fails you only lose that drives data not everything, this also means that as each drive is not really dependant on another they can all spin down and sleep and thus not use power, and when accessing the data or writing, only the drive that is needed is spun up. Then add a parity drive which gives you RAID 5 like Protection, so that you can lose one of any of the drives in the array and still not lose data, then just swap in a replacement drive that is equal or larger than the failed drive and the data is repaired onto that drive. Best of all it runs off a thumbdrive and has modest hardware requirements. As I said it isnt free, there is a free version that support 3 drives, but for the 16 drive version I want your looking at around $180 AUD. But that, an old motherboard, a big case with a decent power supply and I can start throwing old drives into it as they become free and I have a protected NAS that doesnt draw too much juice.

I will let you know ho my testing goes, just waiting for some free time to go ahead and build the array and then try randomly killing drives to see what happens 🙂