DAS vs. NAS: Parsing the difference
Before we launch into a discussion of our various NAS devices, we need to touch on how the storage market has evolved in the past ten years. Back in 2002, an external hard drive was a hard drive with a wall wart, an enclosure, and a USB cable. If you wanted an external drive, you bought one. If you wanted an external drive array with network capabilities, sophisticated backup software, and independent file-sharing or FTP options, you bought a NAS. Gigabit NAS devices were also significantly faster than Firewire 400, USB, or USB 2.0-based external drives.
Ten years later, the balance of power has shifted dramatically. External drives, also known as direct-attached storage (DAS) devices, are often sold in multi-drive RAID configurations, with bundled backup software or useful configuration tools of their own. The advent of USB 3 and Thunderbolt has kicked vanilla external drive performance from teeth-grindingly slow to sprightly. This doesn’t make NAS devices spurious, but it suggests a useful starting point for evaluating whether or not you should consider a NAS product in the first place.
Do you need a RAID?
All three of the products we’re reviewing today are two-bay solutions that can be configured as JBOD (just a bunch of disks), RAID 0, or RAID 1. RAID arrays don’t provide backup protection — the idea that they do is one of the most common backup myths — so are they useful in this context? We think so. Redundant and backup may not be synonyms where data is concerned, but that doesn’t make redundancy pointless. A two-disk RAID 1 ensures that the user won’t need to re-copy the entire array contents across the network in the event of a single drive failure; RAID synchronization is handled internally on the unit itself.
One other potential advantage is drive accessibility. Single-drive units are almost always sold in enclosures that users can’t open without voiding the warranty. Multi-bay products, in contrast, are typically designed to be user-serviceable. Doing so may still void your warranty, but it extends the useful lifespan of the device.
The contenders
We’ve got three separate solutions up for testing today: Seagate’s BlackArmor NAS 220, Western Digital’s My Book Live Duo, and Synology’s DS213+. The following chart compares the three products. As we’ve stated in previous articles, we’re focused on data backup rather than cross-network sharing, though we’ll highlight some of these features as well.
The “cost per gigabyte” field for the Synology NAS assumes a pair of Western Digital Red 2TB drives. One important point to keep in mind when comparing NAS devices is that advertised capacity is typically given as a RAID 0/JBOD configuration; we’ve included the price/GB for both this option and a hypothetical RAID 1.
This chart, however, just scratches the surface of what each device is capable of, and where the differences lie.
Next page: The three contenders, in more detail
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