Ad Terras Per Aspera

Over the past six years I’ve owned only three drives. My oldest of the three, a IBM Deskstar 75GXP, continues to spin although it is now the oldest component in my system; it’s two younger brothers are Seagate 7200.8 and 7200.10.

So, in the past seven years, we really haven’t had much in the way of performance increases. Moore’s Law doesn’t apply here, as performance doesn’t double every two years, and Kryder’s Law (the storage analog to Moore’s) states that storage space per square inch doubles every two years, but has no mention for performance.

IBM Deskstar 75GXP 30GB IBM-DTLA-307030:

• 7200 RPM
• Ultra ATA/100
• 2MB buffer
• 15ms average seek time
• Released 04/2000, approximate cost of $250
• Once called the fastest consumer drive ever

Seagate Barracuda 7200.8 250GB SATA NCQ ST3250823AS:

• 7200 RPM
• SATA 1.5Gb/sec with NCQ
• 8MB buffer
• 11ms average seek time
• Released 04/2004 approximate cost of $250
• Also once called the fastest consumer drive ever

Seagate Barracuda 7200.10 400GB SATA NCQ ST3400620AS:

• 7200 RPM
• SATA 3.0Gb/sec with NCQ
• 16MB buffer
• 8.5ms average seek time
• Released 02/2006, approximate cost of over $300
• Once called the fastest consumer drive ever, and is still one of the fastest

As you’ve noticed, rotational speed (and thus rotational latency) has stayed constant, and bus bandwidth has only increased three fold (100MB/sec six years ago to 150MB/sec two years ago to 300MB/sec now), average seek latency is almost halved, and cache buffers have increased eight fold.

None of that actually states what the performance is, of course. According to hdparm -t (and using the best out of five, with nothing on the system running not even X), the Deskstar is the slowest at 35.82 MB/sec, the 7200.8 coming in at 63.09 MB/sec, and the 7200.10 coming in at 72.00 MB/sec.

May be now it is time for a new law governing computing (and named after myself by myself in bad taste):

McFarland’s Law: The performance of consumer hard drives doubles roughly every six years.