Choosing a hard drive for a Network Attached Storage (NAS) device

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Someone I know is upgrading their local file backup scheme from external hard drives that plug directly into computers, to a Network-Attached Storage (NAS) device.

A NAS is a special purpose computer, sold without hard drives, that plugs into a network rather than a computer. It functions as a file server giving all computing devices on the network a single place to go for shared files. A low end NAS device houses a single hard drive, higher end models contain up to a half dozen (perhaps even more, my budget has never let me even dream past four).

Buying a NAS box requires three decisions: picking a hardware vendor, deciding on the number of internal drive bays and, finally, choosing a specific hard drive to install.

The manufacturer was dictated by the NAS device another person already owned. The plan is to have the new NAS device synchronize files with an existing Synology NAS owned by a trusted off-site person. This may work between NAS devices from different vendors (I have not tried it), but I felt it was safer to keep it all in the family. So, we went with Synology.

Then we opted for a single drive NAS box for these reasons

  • It is significantly cheaper. Single drive NAS boxes are cheaper than dual drive models,  plus there is one less hard drive to buy so you save in two ways.
  • There already was a collection of external hard drives that could handle data spillover in case the capacity of a single drive proved insufficient going forward  
  • As noted already, the long term plan is to backup the most important data off-site to a companion NAS box
  • A single drive should use less electricity, run quieter and build up less heat
  • The data being backed up is personal, rather than business

A business, including someone who works at home, may be better served by a dual drive NAS box using RAID Level one to mirror one hard drive to the other. This is debatable however.

For one thing, RAID data duplication protects from only one type of problem, and there are still many ways that data stored in a RAID box can be lost or corrupted. RAID is mostly an availability thing, not a backup thing. Plus, local backups are only half the story, anyone serious about backing up data also has off-site backups.

Choosing a hard drive for a NAS device used to require a visit to the website of the NAS vendor looking for a list of approved or known compatible drives. But, just over a year ago Western Digital came out with a line of 3.5 inch Red hard drives specifically designed for use in Network Attached Storage devices.

This left perhaps the most interesting decision - whether to buy the 1TB, 2TB, 3TB or 4TB model.

Some might suggest the largest available capacity, after all, hard drives are like closets, your stuff always seem to expand to fill it. Or, you might opt for the capacity you think you need, leaving a bit of a cushion for good luck. Then too, you might calculate the cost per gigabyte of each model and buy the one offering the most bang for the buck.

As a Defensive Computing guy, my priority is reliability. But, according to Western Digital, the reliability specs for all four Red hard drives are the same.

So I opted for simplicity.

My thinking is that a simpler mechanical device is likely to be more reliable than a complicated one. The fewer moving parts the better. Thus, I'm looking for the drive with the least number of internal platters. Fewer tickets in the failure lottery.  

Western Digital, like other hard drive vendors, does not publish the number of platters inside their hard drives. But, there are a couple ways to infer it: the weight of the drive and the amount of electricity needed to power it.

According to the specs, the power needed for Read/Write activity on the Red NAS drives is 4.5, 4.1, 4.1 and 3.3 watts, listed from the 4TB model down to the 1TB drive. The average power at Idle for the four drives follows the same pattern: 3.3, 3.0, 3.0 and 2.5 watts. Clearly there are more platters in the larger capacity drives.

Western Digital only reports an approximate drive weight, one with a margin of error of plus/minus 10%. That said, the drives weigh 1.50, 1.40, 1.32 and 0.99 pounds (again from 4TB down to 1TB).  

Since these numbers are not brutally conclusive, I went looking for reviews of the Red drives. A review from July 2012 by Kevin O'Brien at specifically stated that the drives have 1TB platters.

The decision was clear. We went with the single-platter 1TB model.

Besides having fewer tickets in the hard drive failure lottery, the single platter 1TB model will use a bit less electricity, will run a bit quieter (according to published specs) and should run cooler (always a good thing).

Speaking of environmental issues, Synology offers a great way to save on electricity - the box can turn itself off at night and back on again in the morning. Not to be confused with the hard drive spinning down after a set period of inactivity, this is a function of the NAS box and its DSM operating system.

Nighttime shutdowns may not be an option for college students that need to burn the midnight oil, but for the rest of us, it can be a good thing - as long as you don't forget about the schedule. I had set this up on an off-site Synology box and forgotten about it. Then, at home, I went to download a huge file from the NAS box before going to sleep, figuring the download could run overnight. It wasn't till the download failed two nights in a row that I realized why. Every coin has two sides.

Finally, while finishing up this piece I stumbled onto the fact that Seagate now also offers a line of hard drives custom built for use with NAS devices. Turns out these drives use 1TB platters too, but the lowest capacity Seagate model is 2TB. That's two tickets.

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