Archive: January 15, 2008

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hard drives: faster isn't necessarily faster

Tuesday,  01/15/08  09:13 PM

Okay, so here’s some esoterica for you… on the subject of laptop hard drives.   Please feel free to skip…

Windows being what it is – a horribly inefficient OS which has poor paging algorithms – disk performance tends to be just as important as CPU performance in the overall “feel” of a system.   Historically this is a key reason why laptops have felt slower than desktops; the CPUs are nearly as fast (even with their power management algorithms), but the 2.5” disks found in laptops have been way slower than their 3.5” desktop brethren.

Since carrying around a desktop is a bit awkward, finding a fast hard drive for your laptop is a good thing to do.

So there are four characteristics of a drive which determine its performance.   First you have seek time, the speed with which the disk heads move across the disk to the desired track.   Second you have rotational speed, which affects the latency of waiting for the desired sector to spin under the heads.   Third you have transfer speed, the speed at which bits are moved from the drive to main memory.   And fourth you have the cache size; a larger cache allows the disk to do more reads faster, because read B can be started while read A is being transferred (and for a big cache, read C and D and … can be started too).   These four factors are important in roughly the order I listed them above.

A couple of years ago I began with the “stock” drive that came in my HP nc8230 laptop.   (for longtime readers, yes, that laptop :)  It was a 60GB hard drive, spinning at 5400 RPM, with a 2MB cache.   About a year ago I upgraded to a 100GB hard drive, spinning at 7200 RPM, with a 4MB cache.   Big difference!   In addition to having 40GB more for storing digital slides (!), the drive was noticeably faster, and the whole laptop felt faster.   A good thing.

Recently I began poking around for a new drive, since I had managed to fill my entire 100GB with files.   Plus I thought maybe drives had become faster in the interim.   So what I found is that the largest drive available spinning at 7200 RPM is still about 100GB.   In order to get a bigger drive, I’d have to get a “slower” drive spinning at only 5400 RPM.   How much slower would this drive be?   Not clear.   So in the name of science I ordered a 250GB drive, spinning at 5400 RPM, with an 8MB cache.

Guess what?   It is faster.   Noticeably faster, the whole laptop feels faster.   Which is a good thing.   But, um, it is only 5400 RPM, not 7200 RPM.   What is going on?   Well it turns out there are four factors in hard drive performance :)   And the seek time of this drive is considerably faster than the seek time of the “faster” 7200 RPM drive.   (As a general rule, the larger the capacity of a drive, the faster it seeks, because to access any given amount of data requires less head movement.)   Furthermore the transfer speed is faster (slightly), and the cache is twice as large, allowing more activity to take place in parallel.   The net of all this is that the 250GB 5400 RPM drive is actually quite a bit faster overall than the 100GB 7200 RPM drive, despite having a slower rotational speed.

So – faster (rotation) isn’t necessarily faster (overall).  And yes I am enjoying having an additional 150GB too :)

P.S. You might wonder why the newer bigger drives aren't also 7200 RPM.   I think it is because 1) they draw more power, and 2) they are noisier (whinier).   Both are important factors to laptop users.   So as long as the hard drive vendors can give you faster performance at a lower rotational speed, they’ll do it.


Tuesday,  01/15/08  10:12 PM

Still on my old laptop hard drive, in the process of rebuilding my new one.  (The rebuild doesn't have anything to do with it being faster, or larger, it has to do with an NTFS corruption issue.  But I digress.)  Anyway onward, let's see what's happening...

So Mitt Romney has won Michigan.  Powerline analyzes the state of Republican play.  My main attraction to Romney is that he's a governor.  Really, that is much better preparation for being President than having been a senator.  Plus, he's a successful businessman, and seems to have a really stable family.  If only he weren't a Morman, not that I care much about religious beliefs, but it seems a leading indicator of lack of intelligence... 

Apple!  Whoa.  Did you see the Jobsnote?  I treasure them as performances, not only communications from an innovative computer company.  I'd give yesterday's performance a solid 8, unrelated to the announcements themselves, which I'd give a 10.  

Mahalo has a fantastic 60 second summary of the 90 minute presentation, if you're in a hurry.

So the new Macbook Air will garner the most attention - it is beautiful - but I actually think the iTunes Movie Rental stuff is the most significant.  About a year ago I bought an original AppleTV, I like it, but it hasn't set my world on fire.  The friction of buying movies online from my computer (in my office), waiting for them to download, and then waiting for them to sync to the AppleTV before watching them (in my family room) was just enough to keep it from being used a lot.  Now that is all history; you rent online from the family room, and poof, you start watching it immediately.  And a lot of the content is HD!  I agree with Popular Mechanics that this makes the whole Blu-ray vs HD-DVD issue moot. 

John Gruber analyzes iTunes rental details and makes an excellent point: how about a 27-hour day?

But back to the Macbook Air, yes, it is beautiful.  And I notice it has an option for a solid state disk, 64GB of SRAM masquerading as a hard drive.  As Jobs said, "they're pricey, but they're really fast".  This could be a peek into the future.

After I watched the Jobsnote I turned to Reggie (my cat) and said, "what a great time to be alive".

More techno-lust on my part: the Dash internet-connected GPS.  I want one.  In fact, I've wanted one ever since I had my first GPS in my car, eight years ago.  Someday they'll be built into every car. 

Did you know expensive wine tastes better, because it's expensive?  Yes, apparently.  "Researchers from the California Institute of Technology and Stanford's business school have directly seen that the sensation of pleasantness that people experience when tasting wine is linked directly to its price."  This explains so much.  My taste in women, for example :) 

I wonder if Maseratis drive better because they're expensive?

Glenn Reynolds watched Terminator, the Sarah Connor Chronicles, and I did too.  "Not bad, and Summer Glau makes a surprisingly credible Terminator robot. Well, maybe it's not surprising considering her scarily-credible role as a biologically enhanced killer on Firefly/Serenity."  I found myself rooting for it, I think it wasn't as good as I hoped, but wasn't as bad as I feared.  I'll give it a chance - this could be the first TV series I watch in, well, years and years and years... 

Robert Scoble is on the move again; Microsoft's most famous blogger spent the last year at Podtech, and is now moving to  I like Robert and definitely wish him well.  I must tell you I'm from Missouri on this whole "video podcast" thing, however; I still like text because it can be skimmed.  But I'm an oleosaur. 


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