Some people eat, sleep and chew gum, I do genealogy and write...

Saturday, October 5, 2013

Measuring Up -- Comparing data storage costs

My wife came home from the store with a number of very small containers of ice cream. When I questioned the purchase, she responded that the smaller containers were less expensive per unit than the larger ones. This started me thinking about genealogy and computers (you try and figure that one out, everything relates to genealogy).

We buy many things such as milk and ice cream buy the gallon, the quart or the pint. Interestingly, the price for each size is usually prominently displayed and advertised. In fact, many supermarkets today have posted unit pricing. But when we, as computer-using-genealogists buy data storage devices, the unit cost is rarely advertised and very infrequently even discussed. But there is just as much logic in buying computer memory storage based on unit cost as any other product.

Here are several examples.

All the prices are taken from and differences and variations in the specifications of various drives are ignored for these first examples.

  • Glyph GT 062E - 6 TB - 7200 RPM  $539.00
  • Seagate Expansion 4 TB 3.0 USB Desktop External Hard Drive (STBV4000100) $150.01
  • Seagate Expansion 3 TB USB 3.0 Desktop External Hard Drive STBV3000100 $112.15
  • Seagate Expansion 2 TB USB 3.0 Desktop External Hard Drive STBV2000100 $79.99
  • Seagate Expansion 1 TB USB 3.0 Desktop External Hard Drive STBV1000100 $65.99
  • Seagate Expansion 500 GB USB 3.0 Portable External Hard Drive STBX500100 $54.99

I would have included a Seagate 6 TB drive, but they are not available as yet so I choose a substitute. Usually drives advertised as 6 TBs are really 2 - 3 TB drives in a RAID configuration. The disparity in the price per unit, when you directly compare the drives is obvious. The 1 TB drive is selling for $65.99 per TB. The 4 TB drive is selling for $37.50 per TB. The 3 TB is only slightly less per TB at $37.38 and the 2 TB drive is more expensive than either at $39.99 per TB. So why is the 1 TB hard drive so expensive? Easy, it is the cheapest in total dollars so the unwary buyer will naturally buy the one that looks the least expensive. There are also likely fixed costs of manufacture and distribution that do not change when you sell a larger drive in what is essentially the same box through the same distribution channels. You can see this dramatically in the 500 GB drive which is half the capacity of the 1 TB drive so would be about $110 per TB.

By the way, these are not necessarily the lowest prices you can find on the Web for comparable hard drives. I used these prices because the drives were roughly comparable and to illustrate the differences in unit pricing. 

If you are familiar with hard disk storage and have been purchasing drives for a long time, a 1 TB drive seems huge. Compared to the size of the hard drive in most computers, unless the computer is very new, a 1 TB hard drive seems more than adequate. But if you were shopping on a per unit basis, it would be the most expensive alternative, by far. Except, you might say, for the 6 TB drive that is running $89.83 per TB. The reason for this high price is simple, 6 TB drives are not yet easily available in the marketplace and larger sizes are virtually non-existent except in RAID configurations. That could change dramatically over time, maybe not. There is another technology rapidly gaining on hard disk drives; flash memory drives. Now, remember, the 500 GB drive was even more expensive on a unit basis because they are likely being phased out and not manufactured. 

The best buy? Obviously, right now, the 4 TB hard drive. But what if you don't need all that space, you say? My answer is you will. Think photographs.

So what is the cost of other types of storage? I mentioned flash drives. This is obviously becoming the next technological wave. Many computers are now coming with internal flash drives and small flash drives are ubiquitous. Can they build very large flash drives to compete with the price of spinning media hard drives? Very likely, unless some other technology comes out to replace both. Flash drives have an advantage over hard drives in that there are no moving parts; all of the storage is in chips in the "drives." I guess you can "drive" something that doesn't move (like the U.S. Government for example).

Back to computers and memory storage devices. So how do flash drives compare? Here are some examples:
  • Kingston Digital HyperX Predator DataTraveler 512GB USB 3.0 Flash Drive (DTHXP30/512GB) $599.99
  • Kingston Datatraveler 310 - 256 GB USB 2.0 Flash Drive DT310/256GB $110.00
  • SanDisk Cruzer Glide 128 GB USB Flash Drive SDCZ60-128G-B35 $81.26
  • SanDisk Cruzer Glide 64 GB USB Flash Drive SDCZ60-064G-B35 $44.17
  • SanDisk Cruzer Glide 32 GB USB Flash Drive SDCZ60-032G-B35 $20.84
  • SanDisk Cruzer Glide 16 GB USB Flash Drive SDCZ60-016G-B35 $17.46
  • SanDisk Cruzer Glide 8 GB USB Flash Drive SDCZ60-008G-B35 $9.75
  • SanDisk Cruzer Glide 4 GB USB Flash Drive SDCZ60-004G-B35 $9.86
Larger capacity flash drives, that is larger than 512 GBs, are hard to find and much more expensive. Kingston makes a 1 TB flash drive that sells for over a $1000 if you can find one to buy. 

You can do the math yourself. But notice that the lowest capacity flash drive, 4 TB, is $2.47 per GB and the 128 GB flash drive is only $.64 per GB. But also remember that a TB is 1000 GBs, so the cost of the 128 GB flash drive in TBs is 1000 x .64 or $640 per TB. The prices on flash drives will have to come down dramatically to make them competitive with hard drives, which, by the way, will likely happen as I mentioned. You can see that a 512 GB flash drive (essentially 1/2 the capacity of a 1 TB drive) is over $1000 per TB. 

Flash drives smaller than 4 GB are being given away free as novelties for advertising in many cases. 

These same principles apply to many other types of computer products. So think unit cost and make your choice based on reality. 


  1. Thanks for doing the maths, James. I'll be taking your blog post to our Technology Special Interest group this week. Our topic is gadgets.

  2. Comparing is the best way to save some money and get services at affordable rates.So first compare then buy server space.

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