I've had my WD Elements 1.5TB External HDD for well over a year now, and I'm starting to worry about it's lifespan.
Would it be wise to buy a second one at this point to back up my first one? I've got a lot of data on it and I'm worried that one day I'm going to hop on my computer and it's going to have broken.
If your data is only saved one place, it is not safe.
Read that again. And again.
Always back up your data. If that lone 1.5 TB drive is the only place your precious files are, then you're one bad hard drive away from total loss.
Hard drives are cheap. Do yourself a favor and buy a second one to back up your files.
I wouldn't worry about replacing it at this point. I have hard drives that are 10 years old that still work just fine.
You want to make sure that you take care of it appropriately to make sure it lasts:
Typically when a drive starts to fail you'll notice degraded behavior.
The drive's SMART support will also report problems with the drive. You can find programs like HDDScan to scan the drive for errors and report on the SMART status of the drive, which will report the number of bad sectors.
If you're only using the drive for data storage, the drive is likely to last a very long time, much longer (I would say) than a drive in your PC.
One approach you may want to take is to purchase an external backup unit, such as an iomega ix2-200, or other such network storage devices. You could periodically backup your data to that other device. Of course you could just use the ix2-200 as your 'external drive' if you don't need it to be portable, and it has RAID 1 support so if one drive dies, the data will live on on the second drive. For RAID 1 support, make sure to get twice the storage space you need, as both drives will maintain a copy of the data on the other drive in case one drive fails, so the 4TB model has 2x2TB drives with 2TB of useable space.
A study done at Google found that in the first year of operation the annualised failure rate(AFR)% for disks was 1.7%. For disks aged 2 to 5 years the AFR was between 6% and 8.7%. Ask yourself these questions:
1) If I'm going to do something about this in the future, what do I gain by not doing it now?
2) How mich risk am I willing to accept?
Hard drives use up most of their life during the first 2 years, after that it is a sliding scale towards disaster.
It really depends on hours of usage and the amount of read/writes, my comment is based on it operating 24 7 365.
That being said, a hard drive can fail at any time without warning or SMART warnings, you should always have important data on 2 or more physical drives.
Large hard drives are on the bleeding edge of hard drive technology, I don't trust them like I did 10 years ago.
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Generally external HDD are used for storage more than active use, which would mean that the number of writes to the drive will have been kept relatively low. So in terms of the HDD performance, I would say that unless you have some sort of indication that it is not functioning correctly, the drive will continue to have a comparatively long and fulfilling life until it outlives its usefulness by becoming too small for practical use. In my experience this is usually in the region of 5 years or so.
However...
If the data you store on this HDD is important, unrecoverable information that is important to you, you should ALWAYS back it up. And not on another HDD, which is always the short sighted option people seem to go for, but an actual off site backup that will protect you from theft, fire, flood, etc. The easiest way of achieving this currently is to use cloud storage services such is Microsoft's SkyDrive, Googledocs or maybe even a service from your ISP.
