JonnyWoodman writes:
With today's security threats, periodically backing up data is more important than ever for typical home users. In the past, DVD's were often assumed to be the least expensive media for permanent backups. This was certainly true back when 4.1-GB Hard Drives sold for $120. Under prevailing wisdom, Hard Drives were best for on-line usage, never to be considered for long term archival storage.
Ideally, you should want to have multiple backups. It is useful to have frequent incremental backups, as well periodic snapshots of everything. This implies a lot of data. Selecting the lowest cost media will promote favorable backup habits.
It is interesting to compare storage media based on the cost-per-GigaByte (GB). The trade-offs have changed considerably over time. We now have multiple options to choose from, including Memory Sticks, various optical media such as Blu-ray disks, and external Hard Drives, as well as Cloud Storage options. Of course there are many aspects beyond just cost when choosing media for various purposes, such as access speed, expected longevity, scalability, or physical space needed to store it. However, for just long-term archival backups of typical home users or small businesses, I will assume that access speed is less critical. Cost-per-GB, ease of use, longevity, and physical storage volume are therefore primary factors. The typical storage capacities needed will range from a few GB of user data, up to the size of a typical Hard Drive, perhaps 1-TB or more.
Price comparisons are difficult because you will find a range of prices from various sources at any point in time — and these will continue to change over time. So consider the following to be only a Rough Order of Magnitude comparison based on sampling recent prices at Brick & Mortar Office Supply stores, as well as well known Web-based retailers. Your mileage will vary depending on sales, deals, volume discounts, sources, and etc..
I found the following recent media prices:
- ~$30 for 100 pack of blank DVD's.
- ~$20 for 20 pack of blank Blu-ray disks.
- ~$100 for 2-TB magnetic Hard Drives.
- ~$12 for 64-GB Memory Stick.
- ~$0.35/GB per year for Cloud Storage. Or ~$1.75/GB for 5-years.
DVD's can theoretically hold a maximum of 4.7 GB. But in actual usage, you will not get too close to that because pushing toward the limit increases the chances of a bad burn. In practice, due to the odd sizes of files, you will be lucky to place about 3.5 to around 4.3 GB on a DVD. Let's say about 4 GB on average. Let's not count the one-out-of-four or so that don't burn properly for whatever reason, or which end up having bit errors, etc.. Similarly, conventional Blu-ray disks are rated at 25-GB. But I will assume practical storage on the order of about 23-GB per disk. Cloud Storage has a different price model. Instead of paying-once as with user-owned media, many Cloud Storage firms require continuing payments. For this comparison, I'll assume a nominal 5-year time frame.
So the rough Price Per GB (PPGB) for each media type, in Cents per GB, came out to be about:
- DVD: 8
- Blu-ray: 4.3
- Hard Drive: 5
- Memory Stick: 19
- Cloud Storage: 175
(Prices in US-cents.)
So Blu-ray now appears to be the lowest cost medium, with magnetic Hard Drives coming in a very close second place.
Other types of media still have advantages for particular uses. Although Memory Sticks are expensive as an archival medium, they provide conveniences in other ways. Non-Techies may feel more comfortable with thumb drives than burning optical disks.
Some may like Cloud Storage, but others may not like the idea of paying year-after-year to store their old data, as well as the relatively slow transfer rates over internet. Cloud Storage would have the apparent advantage of off-site storage. However you could achieve the equivalent by keeping your backup media at a different location as well.
DVD and Blu-ray disks are convenient for moderate sized backups because you can easily remove them.
But a 2-TB hard-drive is more compact than the equivalent 80 Blu-ray disks or 500 DVD's plus cases. With the latest external USB Hard Drive docks, you can easily plug-in spare hard-drives without opening your computer case. And backing data up onto a Hard Drive is easier than than making ISO's and burning optical disks — with much higher data-rates as well.
Optical disks are still good for mailing someone a large amount of data. But now it is often faster to use the internet for shipping data.
I did not list double- and triple- density Blu-ray, which are capable of storing 50-GB and 100-GB per disk, respectively. However, you must have a sufficiently capable Blu-ray drive. I would expect an even more favorable cost per GB, thus keeping Blu-ray in the lead by cost. I also did not list various magnetic tape options, since these are not widely adopted by home users.
As far as the comparative longevity of these media, there is little definitive data available due to the newness of the formats, as well as the wide variations in manufacturing quality between brands. It is possible that optical disks may exhibit substantially different final Bit-Error-Rate (BER) statistics than magnetic Hard Drives, due to their intended applications. For example, a bad bit in a video stream may be more tolerable than a bad bit in critical financial data. Blu-ray is targeted at the former, while magnetic disks are normally expected to store the latter. Only time and experience will tell.
So for now, Blu-ray and externally mounted Hard Drives offer the lowest media costs. When considering the combination of cost with ease of usage, externally dockable Hard Drives now appear to offer the best overall convenience and compactness for archival storage.
