Only eighteen months have passed since I wrote the paper on backing up photographic images, but there have been some changes that affect the off-site component of the backup strategy that I proposed in that paper. The biggest difference is the price reduction of one terabyte disks. It’s now hovering close to a hundred bucks a drive. It’s actually cheaper to buy a 1 TB disk than an 800 GB LTO4 tape cartridge! So tape is just not economical any more.
Add the new cost reality to the fact that disk-to-disk backup offers the convenience of recovery of full tape backups with the speed of updating of incremental backups, and I figured it was time for me to change.
I have about 5 terabytes of data to back up. I could, and have, used individual 1 terabyte disks, sheathed in metal canisters from Granite Digital that offer mechanical and electrostatic protection without increasing the size of the packaged drive enough to keep them from fitting in a standard size safe deposit box. There’s a link to the canisters at the bottom of this post.
To deal with 5 terabytes of data and have some logic to the file arrangement and some room to expand the contents of various directories in the future, you need to use six or eight drives. Double that number to have one set at home and one set at the bank. That’s a lot of drives to deal with. However, the worst part is attaching all the drives to computers. USB drives aren’t at their best when connected through a USB hub (although that can work, if you don’t mind a few glitches). For best reliability, USB drives should be connected directly to the computer. I don’t know of a computer that has enough USB ports so you can connect a mouse, a keyboard, a hub, and six or eight USB drives directly. So you need to use a hub and deal with the hiccoughs, or spread the drives out among several networked computers. Neither approach is untenable, but neither is a lot of fun.
There is a product called the Drobo that has the potential of easing the pain. It’s a fairly small box that takes four bare SATA disk drives, and connects to a computer through either a USB or a FireWire port. It makes sense to attach teh Drobo to a computer; there’s a device available that turns one or two Drobos into network attached storage, but it’s purportedly really slooooow. There’s a micro-computer in the Drobo that looks at the characteristics of the drives that you’ve put into the box, and decides, according to its internal, unchangeable rules, what’s the best way to use them.
I would prefer some direct control, but the logic that it uses is pretty straightforward. If there’s only one disk installed, it makes that disk available. If there are two, it mirrors them (RAID 1) makes it look to the attached computer like you have one disk the same size as the smaller of the two disks installed. If there are three or four disks installed, it sets itself up as a RAID 5 array. With three disks it looks to the attached computer like there is a single drive of twice the capacity of the smallest installed drive, and with four disks it looks to the attached computer like there is a single drive of three times the capacity of the smallest installed drive. For off-site backup, it would be nice to tell the box to forget the redundancy and just make it all look like one big drive whose size is equal to the sum of the capacity of all the installed disks, but that’s not possible. On the other hand, having the RAID 5 capability means that one of the drives can fail, and you’ll still have your data intact.
After you’ve gotten the data loaded onto your Drobo, you can shut it down, pull the disks, and stick them is a safe deposit box. I suggest wrapping them in some padding and some antistatic material. At the end of this post, there’s a link to the silicone caddies that I’m using.
The Drobo costs between $400 and $500. That seemed like a bargain when big disks were $400 a pop, but doesn’t seem so cheap now that they cost a quarter of that.
The biggest SATA disks you can buy right now are the Seagate 1.5 TB drives. I was tempted, but poked around on the web and found a lot of upset users with credible complaints, so I decided to go with Samsung and Western Digital 1 TB drives. Shove four such drives in a Drobo, and you have a little over 2.7 TB of storage. Two Drobos should do the job for me.
So here’s my plan:
- Load two Drobos with 1 TB drives
- Set up an automatic backup procedure to take all the server on-line backup files and periodically write them to the Drobos
- Every so often, swap the disks out of the Drobos for another set
- Take the first set to the bank and put them in a safe deposit box.
In my next post, I’ll give you a play-by-play, and then I’ll draw some conclusions.
Metal disk canisters http://www.granitedigital.com/35aluminumdriveshieldsdrivemechanismprotection.aspx
Silicone disk caddies http://www.granitedigital.com/25and35siliconedriveshieldsdrivemechprotection.aspx
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