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Hard Drive Speeds

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February 5, 2011 5:51:57 PM

If I could indulge on the collective mind of the internet, I'd like to know how RPM affects transfer speeds with exact numbers.
(Example: If i transfer files between my 2 500 GB HDD at 7200 rpm and 3.0 Gb/s with 32 MB cache, the speeds range from 60 MB/s to 130 MB/s). Ignore speeds from Master Drives like your hard drives carrying your OS. I am assuming INTERNAL SATA drives.

There are a few questions to go along with this:
-Does HDD size affect the speed assuming all other factors are constant? assuming a 500 and 750 GB HDD both have the same number of disks and rpm, would the 750 GB one be faster just because the rotational speed is the same and more data is packed in the same surface area assuming the data on each is in the same place? I'm just thinking of tangential speed = rotational speed * radius.

-If I transfer from Hard Drive to Hard Drive (assuming same models), is the write speed on the destination hard drive the limiting factor?

-If I transfer files through an internal network, would the network speed be the limiting factor?

If you wish to post test results for your hard drive speeds, make sure you did not transfer to or from the hard drive with the active OS.

Please include your Hard drive capacity, cache, RPM, and Interface (SATA I-III) for both THE SOURCE AND DESTINATION DRIVES when posting transfer speeds.

More about : hard drive speeds

a b G Storage
February 5, 2011 6:15:46 PM

1) Yes, HDD size will affect speed, exactly as you said, in a larger drive, more data is packed in a smaller space which reduces access time as its closer together. The reading head of the drives must move a less distance between chunks of data.

2)Yes, I think the write speed of the destination drive will be your limiting factor, just like when you use the internet for Download and Upload, the upload from the server limits your download. Same goes for storage devices (I think). Not 100% sure though.

3)It depends on the network, if the network is faster then your HDD's transfer speeds, then the HDD's are the limiting factor. If the network is slower then the network is the Limiting Factor.

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February 5, 2011 6:28:59 PM

blackhawk1928 said:
3)It depends on the network, if the network is faster then your HDD's transfer speeds, then the HDD's are the limiting factor. If the network is slower then the network is the Limiting Factor.


Think of a normal home wired network. I don't know much about the different category ethernet cables and their effects on performance, but I guess we can assume 25' cat5e ethernet cables to your average switch or router. Normally I'd assume that network speeds are almost always slower because I think of 10-100 Mbit connections which would mean a bottleneck of 1.25 to 12.5 MB/sec. I don't know if wireless could be faster, but I typically think of wireless as much slower.
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a b G Storage
February 5, 2011 7:42:55 PM

Well the majority of people I know have home networks of 100mbps Full Duplex hardwired. And a 54mbps wireless network.

If the network is a 100mbps Full Duplex, transfers will be 200Mbps theoretically so
200÷8=25MB

^Most average HDD's exceed 25MB transfers by a huge margin...I know my HDD does a max of 140MBps transfer rate which would be:

140÷25=5.6

So my HDD exceeds a 100Mb network by almost 6 times....So a good generalization from my POV is that the majority of the time in a home, the network bottlenecks.

I however have a 1Gbit network Full Duplex so my transfer speeds 10times more.

2000÷8=250MB <So for my network, its transfers exceed my storage devices transfer rates so for me the storage is bottleneck, not the network. My wireless is 150Mbps also.
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