You may be absolutely right. CPU clock frequency certainly has hit a wall at around 4GHz. However, this hasn't stopped CPUs from getting progressively faster. I know this is mixing apples and oranges, but my point is that no matter what limits or barriers computing technology hits, someone comes along and finds a way to engineer around it.
I have no idea what storage technology will look like years from now, but I will be very surprised if the limitations you've listed have held back advances in storage devices. No idea what those devices will look like or how they'll work. If someone told me roughly 10 years ago that I would be using multi-core processors at the same clock speed as my Pentium 4, I would have probably scoffed at the idea. Here we are. I'm a drinker, not a prophet ;-) Like I said, I've built my system planning to upgrade with bigger capacity drives when I start running out of space rather then adding more drives. This is almost certainly unrealistic. I've always built my systems around planned upgradeability, but whenever it does come time for an upgrade, it never makes sense to do so. It's usually much more cost effective to just build a new system with newer and better technology. It should take me a long while to fill up 9TB, but there was a time when I thought a single gigabyte was a ridiculous amount of storage too. Eric On Apr 8, 2010, at 11:21 PM, Erik Trimble wrote: > Eric Andersen wrote: >> I find Erik Trimble's statements regarding a 1 TB limit on drives to be a >> very bold statement. I don't have the knowledge or the inclination to argue >> the point, but I am betting that we will continue to see advances in storage >> technology on par with what we have seen in the past. If we still are >> capped out at 2TB as the limit for a physical device in 2 years, I solemnly >> pledge now that I will drink a six-pack of beer in his name. Again, I >> emphasize that this assumption is not based on any sort of knowledge other >> than past experience with the ever growing storage capacity of physical >> disks. >> >> > Why thank you for recognizing my bold, God-like predictive powers. It comes > from my obviously self-descriptive name, which means "Powerful/Eternal Ruler" > <wink> > > Ahem. > > I'm not saying that hard drive manufacturers have (quite yet) hit their > ability to increase storage densities - indeed, I do expect to see 4TB drives > some time in the next couple of years. > > What I am saying is that it doesn't matter if areal densities continue to > increase - we're at the point now with 1TB drives where the number of > predictable hard error rates is just below the level which we can tolerate. > That is, error rates (errors per X bits read/written) have dropped linearly > over the past 3 decades, while densities are on a rather severe geometric > increase, and data transfer rate is effectively stopped increasing at all. > What this means is that while you can build a higher-capacity disk, the time > you can effectively use it is dropping (i.e. before it experiences a > non-recoverable error and has to be replaced), and the time that it takes to > copy off all the data from drive to another one is increasing. If X = (time > to use ) and Y = (time to copy off data), when X < 2*Y, you're screwed. In > fact, from an economic standpoint, when X < 100 * Y, you're pretty much > screwed. And 1TB drives are about the place where they can still just pass > this test. 1.5TB drives and up aren't going to be able to pass it. > > Everything I've said applies not only to 3.5" drives, but to 2.5" drives. > It's a problem with the basic winchester hard drive technology. We just get > a bit more breathing space (maybe two technology cycles, which in the HD > sector means about 3 years) with the 2.5" form factor. But even they are > doomed shortly. > > > I got a pack of Bud with your name on it. :-) > > > > -- > Erik Trimble > Java System Support > Mailstop: usca22-123 > Phone: x17195 > Santa Clara, CA > Timezone: US/Pacific (GMT-0800) > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
