Why your NAS box needs RAID

You’ve just purchased a shiny new NAS box and you’ve gone for the big kahuna: The D-Link ShareCenter DNS-343-4TB, which comes equipped with four 1TB hard drives. That ought to be enough to handle all of your multimedia storage needs. You connect it to your PC and expectantly look for four network drives to appear in the Windows Explorer window. Instead, the device’s full storage capacity appears as a single drive within the Network section of Windows Explorer. What happened?

Don’t worry. You’re looking at a RAID, or redundant array of independent disks. And thanks to the power of RAID, you can tap into all 4TB of storage at once.

The difference between an ordinary drive and a RAID array is like the difference between moving into a new apartment all by yourself and enlisting a bunch of burly buddies to help. Splitting a workload normally delegated to one drive (you) among a number of hard drives (you plus your friends) lets you access data (move boxes and furniture) a lot faster.

If you’re familiar with the BitTorrent peer-to-peer file sharing protocol, you already understand the concept: Retrieving a file from multiple sources means you can pull different parts of the file from multiple entities simultaneously. Suppose each source in a network is limited to a transfer speed of 10MB per second, and you’re trying to download a 1GB file. Downloading it from one BitTorrent source would take 1 minute and 40 seconds. Downloading from 10 sources simultaneously would take 10 seconds: 10 sources, 10MB per second each, 100MB per second, or 1GB in 10 seconds.

Replace "BitTorrent sources" with "hard drives," and you get the general concept of RAID — mostly.

RAID doesn’t merely offer better performance. It also offers redundancy and storage capacity. A RAID array not only allows you to combine a number of physical drives into a single storage volume, it also reserves a part of this combined space to create what’s known as a parity bit. This gives you redundant data storage — an automatic backup, if you will.

A parity bit is like a lifejacket. It’s a little extra data that makes it possible to reconstruct your stored information if any of it goes missing. Suppose you’ve set up the NAS device in a RAID-5 array. Now, suppose one of your hard drives goes to that great scrap heap in the sky. If you ran it as a single drive, guess what? Your data would be gone forever. Run it in a RAID-5 array, and it becomes part of a bigger unit — your data is safe. Once you slap a replacement hard drive in the dead drive’s place, you’ll regain the ability to suffer total drive failure without losing any data.

As far as network storage goes, RAID is a critical part of the equation to make sure that your files are accessible across your network quickly and safely. In my next post, I’ll explain the various types of RAID configurations, including the pros and cons of each.

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