Slashdot Mirror
Petabyte Storage Array
knight13 writes "Engadet is reporting that EMC is rolling out a petabyte RAID array. From the article, "And if you're ready for that level of storage, there's now someplace to get it: EMC has launched its first petabyte array, a version of the company's flagship Symmetrix DMX-3 system that includes nine room-filling cabinets of drives." The price? A mere $4 million."
Interesting calculation: If you live 80 years, that's 435.5 KB per second -- enough for a TV-quality video of your entire life.
Be relentless!
I was just thinking about how 4 years ago you could build a terabyte array for about $5-10,000 down from many millions 8 years ago. Today, you can get a terabyte for less than $500. In a few years, a petabyte is only going to cost $5,000. If you just buying space for future growth, it seems like a total waste of money.
Let's assume for a moment that the average lifetime of one hard disk in this petabyte array is 6.5 years. Since there are 2,400 hard drives, that means that once this thing has been running for a while, you will be replacing, on average, one broken hard drive per day, for the entire lifetime of the array. That's about $350 per day in replacement parts alone!
Only if you use Enron math. You have to pay $25 per employee per hour either way. The only thing that matters is what you mentioned as a side note, revenue from customers lost during the outage. If whatever system relies on this backup is generating you $1,000,000 per hour, then an array like this would pay for itself in one four-hour outage. But, that doesn't take into account opportunity cost: you could still be better off if you put that $4 million to use generating revenue; if it made back more than the outage costs you you're still on top.
All's true that is mistrusted
The faster a disk spins, the more disk surface is exposed to the magnetic field used to write to the drive, so the less storage you have. Disk rigidity is important for two reasons - it limits how close the read head can get and it limits how precisely you can know how much disk surface has been visible. The faster you can either read magnetic fields or generate them, the less disk you need to write to, thus increasing storage. The distance of the read head determines the surface area exposed to the magnetic field on writing, so determines how far apart your data must be to not overlap.
A trivial question might be: Using a standard, existing hard disk (but modifying the controller as necessary) increase the capacity of a hard drive? The answer is "probably".
One way to do it would be to add enough RAM such that a fairly substantial portion of the disk can be held in ramdisk on the controller. Because you are then not reading and writing to the disk directly, but going through ramdisk, the speed of the drive becomes much less important. If you slow the drive down substantially, whilst writing to it at the same speed, the data won't be smeared over the disk as much, so you should be able to increase the density.
In practice, as disk manufacturers don't design their disks with that kind of mod in mind, you are very likely to run into significant problems with defects on the surface that simply aren't visible at 7200 or 15000 RPM. Other problems, such as stability (drives depend a lot on gyroscopic effects and aren't built to go slow), may also limit how much you can cheat on the density.
Another option would be to seriously cool the read/write head, so that you could flip the magnetic state faster. Again, you're limited. Mechanical devices don't like being freeze-dried - even when they ARE dry. However, you may be able to get some improvement that way.
If you're just looking for ANY increase in capacity, then that's trivial and requires no engineering (but some programming). Modern computers are very fast, compared to modern hard drives. If you have one physical sector per physical track, then break down the structure entirely in memory, you eliminate the need for inter-sector gaps, physical sector headers, etc. You might be able to squeeze out another 10%-15% by this method, which isn't a whole lot but isn't bad for the effort it would take.
There are very likely other mods that hard disk manufacturers could use, but which would be totally beyond anyone doing homebrew stuff. The platters probably aren't using the absolute ideal materials - let's face it, they're in business to make money and there are far more home buyers wanting cheap drives than there are perfectionists wanting perfect drives. I suspect there are other areas they could improve on, using existing technology, but won't because it's not economic.
That's probably why you see bursts of improvement. When there's a massive enough need for the extra storage, it can be achieved. When there isn't, it's not worth the extra investment.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
>What if someone wanted to make a photo album with 1 picture for each person on the planet?
How about this, limit the sample to women aged 18-35, but take several photos? Maybe even more space could be saved by taking off the extra clothes...