314GB plus 20TB

The context isn’t that important, but that was recently noted as the RAM and hard disk basis for a particular database.

For some reason, it struck me two ways:

Today, that isn’t all that much

Checking Fry’s for PC-level prices, for name-brand equipment, I see that you could get 314GB of high-speed name-brand RAM (actually 320GB, since it’s  8GB cards) for $1,600 (40 cards, each $40)…and 20TB of internal 7200RPM hard disks for $1,090. If you wanted solid-state storage, it would cost a lot more (not surprisingly): $27,300 (at $350 each for 256GB SSD modules).

So figure $2,700 for 314GB RAM and 20TB storage. Oh, plus a modest amount for the computers to hold the RAM, the RAID enclosures (and extra drives–let’s add another $500 for 50% redundancy)…maybe, what, $10K altogether? Of course, that’s PC-level equipment, but still…

And it wouldn’t take up that much space.

Just 24 years ago, that would have been essentially impossible

Looking back at 1988 prices, I find $63/megabyte for RAM (but on three megabyte cards, so you’d need a bunch of cards, so figure $5.12 million for the RAM (to say nothing of what you’d need to mount 100,000 cards).

Hard disks? A 2008 PC World story claims that a good price for PC-level hard disks in 1988 was $8,755 (in 2008 dollars: figure $4,990 in 1988 dollars) for a 150MB drive. That might be true, but that’s because 150MB was a huge disk for 1988 PCs. More realistically, the Seagate 251 offered 40MB for $400.

You’d need a mere half million of those Seagate drives (which sure didn’t spin at any 7200RPM!) for 20TB total capacity–and you’d spend $200 million to get there.

Let’s say $206 million total.

Consider the ratios

RAM prices pretty much follow Moore’s Law, since they’re integrated circuits. So the price for 314GB in 1988 was 3200 times what it is in 2012. (Ignoring inflation…let’s just do that for now.)

3200:1–a pretty impressive ratio!

Except that hard disk development has consistently been faster than Moore’s Law. Even with today’s shortage of hard disks (those 2012 prices are higher than they should be, thanks to weather-related issues), the price for 20TB in 1988 was 183,486 times what it is in 2012–or, including 50% more storage in 2012 for RAID reliability, call it 125,000.

125,000:1–now that’s an impressive ratio!

[Want solid-state storage instead? Figure about $27,300 in 2012–a lot more than $1,090 or $1,600 with 50% overage. Which suggests that the real Moore’s Law change should be about 7300:1, not 3200:1.]

Still, 125,000 is impressively more than 7,300.


Ignoring the much faster performance of those 2012 hard disks, each of which has a RAM cache almost as large as the Seagate 1988 disk (32MB).

Ignoring the much faster performance of that 2012 RAM.

Ignoring the reality: The system mentioned is certainly not running on PC-level equipment, although my understanding is that Google, at least, does use vast arrays of PC-level hard disks (my understanding could be wrong). It’s not realistic to have that much RAM on a PC for physical reasons, for example…

Ignoring the limits: Well, actually, the only limit even in PC terms is that Windows 7 [Ultimate, 64-bit version] can “only” address 192GB of RAM. (The limit for hard disks is apparently 256TB, so that’s not an issue…)



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