Gigabit ethernet + TC doesn't mean gigabit transfer rates to the TC drive..

Question

Alright.... I've spent a ton of time trying to figure this out (probably more than I should have) and I thought I'd post my findings so that either a) I'll save someone else time out there or b) someone can tell me I'm a complete moron
So I had an airport extreme. I replaced it with a Time Capsule. I have a Windows (boooo) PC connecting directly to my TC using a gigabit ethernet card (which I bought specifically connect it to the TC) so (I thought) I could enjoy gigabit transfer speeds to the internal hard drive from the wired PC. I had some fun plans of shoving my itunes directory on the TC and letting appletv sync (yes through my pc) and keeping lots of videos there, etc. Who cares - it'd be at gigabit speeds! But, in reality, things didn't quite work that way (though my itunes directory does still live on my TC...for now).
Well, I had a semi-unique situation to do some pretty massive testing because I have 2 gigabit network cards, 1 100mb network card, and a wireless-n network card and two internal hard drives - both very fast. I also tried Cat 5, Cat 5e, and a Cat 6 cable.
And here's what I (think I) figured out:
The hard drive in TC can not achieve gigabit transfer speeds. Your transfer rates will be limited by the IO to the hard drive. In fact, it can't even come close.
Using my "fastest" setup - so Cat 6, fastest internal drive, gigabit ethernet, and transferring a file exactly 1 gig in size I was able to have a sustained transfer rate of 140 megabit per second - that's 17.4 MB/s for folks not wanting to do the math (that's reading FROM the TC. Writing TO the TC dropped the speed down to 106 megabit/second or 13.35 MB/s). Going to a 5e cable knocked that down to 130 megabit a second. Putting in a Cat 5 cable knocked me down to 110 megabit a second. Switching between my two gigabit network cards did nothing. Switching my cards between two computers did nothing.
Now, just changing the above setup to use my 100Mb network card resulted in these results: 67 megabit read (8.4MB/s) and 65 megabit write (8MB/s)...
And using wireless N, I got about 10MB/s up and down.
And just as a final test, connecting my two computers together using the 2 gigabit network cards through the TC, I was able to achieve standard gigabit speeds.
SO what does this all mean?
I think the IO to the hard drive in the TC can only read at about 140 megabit/s and write at about 110 megabit/s. I'm not sure if it's the HD itself or how it's connecting to the TC - but that's why I'm not aware of anyone getting faster transfer rates to the drive in the TC (maybe you guys are?). The gigabit ports themselves are fine - and if you're doing anything from one gigabit port to another gigabit port you'll be fine.
So stop beating yourself up trying to find some elusive XP specific issue with gigabit transfer rates (though vista had a problem - shocker), or that you must have a defective gigabit card (which is why I have two cards now instead of one :)), or that your cable must be bad ("maybe my cat 5e isn't good enough?")... it's just this drive ... or how the drive is connecting to the network - can't handle the gigabit speeds.
Unless someone else out there has another explanation? Do these speeds mesh with what you're seeing in "optimal" situations? Or maybe there's just a throttle switch for goobers like me using Windows instead of MacOS!

Answer 1

Hi,
the interfaces available today which connect your drives integrated electronics to your computer can handle that speeds. but the drive itself is limited by the mechanical things going on in there
You can get such transfer speeds if the data you request is in the cache of the drives internal electronics for example. Some drives have 8 MB of cache memory. So if you request to read or write less than 8 mb and (in the read case) you are lucky enough to have those few megabytes cached then you may get that performance
Regards,
somi