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SATA transfer speeds

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November 10, 2009 1:24:17 PM

I am using SATA hard drives rated a 3G transfer rate but only see 30-32M being moved. The system is a shake and bake w/ AsUS P5Q Delux M/B, 4G RAM, 2Dou processors o/s is Windows 7. Is this a norm or is there something I can do to increase the performance. The drives are Seagate Barracuda's, 1.5T and 2T. Backeup takes forever.

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a c 342 G Storage
November 10, 2009 1:52:44 PM

In tests I've seen here at Tom's and elsewhere in the past, based on finding the AVERAGE data transfer rate for a long series of data moves from all over the disk, the average transfer rate for SATA drives is somewhere in the 40 to 75 MB/s range. So your value around 30 MB/s is a bit lower than expected. However, the 3Gb/s (roughly 350 MB/s) spec for SATA II is the Maximum BURST rate for data transfers to and from the disk platters, and definitely NOT the long-term average transfer rate through the entire system. In fact, typical real average speeds for SATA II are not much different from what can be done by older SATA units, and much of that limit is not the drive unit but is really other components of the computer system. Those outside-the-drive bottlenecks are a real challenge for companies introducing the new 6Gb/s SATA systems.
November 10, 2009 5:26:56 PM

Thanks for the info. Kinda expected the performance to be a little slow. I have since checked the hard disk speeds and found the test indicate up to 80mb/sec. What got me looking at this was the performance info from win 7, the lowest score on the report was the hard drive @ 5.9. All of the other areas had incresed with the change to a 64 bit system.
Thanks agin for your reply.
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a b G Storage
November 10, 2009 5:53:30 PM

40-75 sounds slow - typical modern SATA drives are more like 80-120MB/s. What model of hard drive do you had, and how are you testing the speed?
November 10, 2009 6:12:31 PM

It also depends on how you measure your speed:

If you copy from the drive to the same drive, your speed will decrease a lot.
If you copy many small files, the speed will decrease.
If your drive is fragmented a lot, your speed will be low.

You can run some tests (like HDTach) to see what's your real limit.
November 11, 2009 12:03:03 AM

cjl said:
40-75 sounds slow - typical modern SATA drives are more like 80-120MB/s. What model of hard drive do you had, and how are you testing the speed?


Thanks for you response,
The h/d is a Seagate Barracuda model ST32000542AS and is 2T total size. The figure I gave was monitored during backup to a simular internal h/d. What made me look at this was the windows performance report which rate the h/d at 5.9, the slowest device in the system. I had been running win 7 RC 32 bit, but when I loaded Win 7 release ver I went to 64 bit system. That change caused all of the performace subscores to increase about 25 to 30 %, except for the h/d which stayed about the same.

Since then I've tried several tool to check speed, the best i've found so far that works w/windows 7 is HD Speed. It reported regular operation w/64kb blocksize sequential averaged 109.3 MB. Random block size testing burst averaged 172.5MB.

This was under normal operation, no software or devices were disabled.
a b G Storage
November 11, 2009 12:31:32 AM

Those numbers sound about right then. 109MB/s is in the right range for a modern drive.
November 11, 2009 2:25:45 PM

ctsalley said:
I am using SATA hard drives rated a 3G transfer rate but only see 30-32M being moved. The system is a shake and bake w/ AsUS P5Q Delux M/B, 4G RAM, 2Dou processors o/s is Windows 7. Is this a norm or is there something I can do to increase the performance. The drives are Seagate Barracuda's, 1.5T and 2T. Backeup takes forever.


you are limited by the USB bus speed. if you want speed for external back-up hdd use eSata or FW 800.
November 11, 2009 2:28:14 PM

correction....the above response applies only to an external hdd connected to USB 2.0 or FW 400. if you are using an internal hdd it might be a driver issue.
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