Choosing the Right RAID Level for Your NAS Box

In the world of computer storage, RAID is the gift that keeps on giving. We’ve already looked at a RAID arrays in general and, more importantly, how a network-attached storage device that uses this method for combining hard drives can be an invaluable part of your network. But as for the specifics of what RAID can do, that’s dictated by the type of storage array you select.

RAID configurations are called levels. New ones seem to appear all the time, so how’s a computer enthusiast to choose? Allow me to help. Here’s a list of the RAID levels available on D-Link’s top-of-the-line DNS-343-4TB ShareCenter network storage system (all but RAID-5 are also available on the DNS-320 and DNS-325):

JBOD: Short for “just a bunch of disks,” a storage configuration set to JBOD mode isn’t really considered a RAID array per se. The DNS-343-4TB comes with four 1TB hard drives. Set the device to JBOD mode, and it will automatically arrange the drives in a giant, 4TB volume. Invisible to you, the NAS box concatenates the disks together. Data isn’t split across the disks for any kind of performance boost or data redundancy; it’s written sequentially from one disk to the next.

RAID-0: Woosh! That’s the sound four hard drives make when you arrange them in a performance-maximizing RAID-0 array. Level 0 is akin to hiring more workers to perform a time-intensive task: By splitting the work across multiple hard drives, you can have them contribute their maximum individual speeds to fulfill part of a desired task. It’s also the fastest RAID level, but it comes with the largest trade-off: If one drive fails, all your data is wiped out.

RAID-1: If you’ve heard of a RAID-1 array as being the “backup” of RAID arrays, you’ve heard a half-truth. Here’s the deal: In a RAID-1 array, whatever you do to one hard drive is automatically replicated to a second. Sounds like the perfect backup, right? All of your files from drive A are on drive B, and if drive A dies, then you can immediately switch over to drive B with nary a bit of data loss. So far, so good, but what if you accidentally perma-delete a folder or otherwise corrupt a large chunk of data on drive A? The problem is replicated on drive B, and you’re out a double-dose of data. RAID-1 is hardly as fast as RAID-0, but it can survive a drive crash.

RAID-5: A RAID-5 array is faster than a RAID-1 array, but not nearly as fast as a RAID-0 array. It requires at least three linked hard drives to work. The total size of the storage volume equals the size of the smallest hard drive times the number of disks in the array minus one. For example, four 1TB hard drives in a RAID-5 array will give you 3TB of combined storage.

The extra terabyte is used for "parity," split across the entire four-drive set. Parity refers to information that can be used to rebuild the contents of the entire RAID-5 array should one drive stop working. If two drives fail simultaneously, all your data is toast. But a RAID-5 array can suffer the loss of one hard drive without issue. As long as you replace that drive and let your NAS box rebuild the array (and parity) across your drives, you’ll be just fine.

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