Drive Reliability versus Capacity


Today’s Question: I’m now up to over 530,000 images and so have moved from 4TB to 8TB external drives to house my images, both active and back-up. Anything you can offer regarding reliability, performance, or anything else between 4TB & 8TB? Just wondering if I might be safer and/or better off spreading over more 4TB rather than using the 8TB.

Tim’s Quick Answer: There are quite a few variables that affect hard drive performance and reliability, but in general I would say that storage capacity is not a significant factor to consider. I would opt for the larger capacity hard drive for convenience, all other things being equal.

More Detail: When choosing a hard drive, the two primary concerns are performance and reliability (after having chosen the required storage capacity). Performance is not too difficult to get information about. Reliability is a bit trickier to consider.

In concept determining the performance of a hard should be relatively easy. In reality, getting this information can be rather difficult. If at all possible, I recommend tracking down the sustained transfer rate for the drive. Admittedly, many different software tools for testing sustained transfer rate differ in how they perform the test. If possible, I therefore recommend finding independent test results from a single source comparing various drives. I’ve long used PC Magazine’s reviews to try to obtain this performance data, starting here for reviews and more:

For reliability, you could track down the mean time between failure (MTBF) information that is sometimes available from hard drive manufacturers. It can also be helpful to look into reliability data from third-party sources. For example, while it doesn’t cover a wide range of hard drive brands, I find the stats provided by Backblaze to be interesting, especially in the context of seeing how different manufacturers perform in terms of hard drive reliability. You can find the 2019 annual stats from Backblaze here:

The references above are just a starting point, of course. But in the context of today’s question, the bottom line is that I would choose hard drive capacity based on storage needs, and then choose a specific drive based on performance and reliability data to the extent that is possible.