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Hard Drive Question
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Fresh-Faced Recruit
Join Date: Dec 2006
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I just bought a Newer Tech miniStack case and put my 120GB, 7200RPM drive into it to hook to my 24"iMac.
I did some testing. Maybe the results are obvious and I just don't understand, sorry in advance if that is the case.
Copying a 5.73 GB folder From miniStack to iMac drive
USB2 - 4 minutes 58 seconds
Firewire 400 - 2 minutes 56 seconds
Duplicating the folder directly on the iMac drive, with the miniStack disconnected from the computer.
5 minutes 58 seconds.
Why would duplicating the file on the internal drive be slower then copying from the external drive? Even USB2? In all three tests I was writing to the internal drive.
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Senior User
Join Date: Dec 2005
Location: Minnesota
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Because your reading and writing to the same drive versus reading from one and writing to another. How much memory is on the iMac?
Randy
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Senior User
Join Date: Mar 2007
Location: San Jose
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I've found performance varies considerably depending how full the disk is as well (slows down substantially as the disk fills up). But yes, reading and writing to the same disk will be much slower. A fairer test would be duplicating the same file on the external drive.
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Forum Regular
Join Date: Aug 2005
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Originally Posted by newmacnow 
120GB, 7200RPM drive
I did some testing.
Copying a 5.73 GB folder From miniStack to iMac drive
USB2 - 4 minutes 58 seconds
Firewire 400 - 2 minutes 56 seconds
Duplicating the folder directly on the iMac drive, with the miniStack disconnected from the computer. 5 minutes 58 seconds.
Why would duplicating the file on the internal drive be slower then copying from the external drive? Even USB2? In all three tests I was writing to the internal drive.
To expand on a previous answer: it's the difference between using one set of heads, and two.
When you copy from one drive to another, the source drive's heads can stay in position reading the file continuously, while the target drive's heads can be continuously writing.
Now when you duplicate on one drive (or copy between two partitions on the same physical drive) then the one set of heads has to continually shuttle back and forth between reading one area -- shuttle -- writing to the destination -- shuttle -- reading -- shuttle -- writing.
The access time between each read and write is what costs you the extra 3 minutes vs. FIrewire.
Thinking about this for a second, the next conclusion is: when you are doing large projects (Photoshop. FinalCut, Motion, digital audio, etc) you can see how important it is to put your data on a separate physical drive from the boot drive -- because the swap files, which are usually on the boot drive get accessed ALL the time, so putting the data and the swap on different drives maximizes your performance. If you can, you can split up Data, System (swap) and Photoshop Scratch space onto three different drives for even better performance.
Oh, and your test shows why "400 Mbs' Firewire kicks "480 Mbs" USB 2.0's can all around the schoolyard. USB relies too much on the CPU of the Mac to manage the transfer, so it can't sustain high transfer rates, esp. when there is contention for processor cycles.
Thanks
Trevor
CanadaRAM.com
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