I have a system with three hard drives. Two 500Gb Seagate pipeline 2 hard drives. (One of which I boot up with. The bootup hard drive has around 380gb free space) and one Samsung HD103UJ Hard drive which I have all my media stored on. the Samsung drive is almost full with about 15gb free space.

My motherboard is an ASUS M5A78L-M/USB3 with 6 SATA ports and I have a modest 4gb RAM. Yesterday I had some important files (about 20gb worth) which I needed to copy from my Samsung 1Tb to my primary boot drive. I was astonished at the data rate in Windows 8.1 - It was copying at a rate between 1Mb and 2Mb per second. I just gave up after 20 minutes. That is one fifth of the speed of USB 2 and I can download files from the Internet much faster than that! This isn't a new phenomenon either! I have been noticing these data transfer speeds ever time all three hard drives are plugged in at the same time.

I hope I have given enough information and if anybody has any suggestions why this data rate is so slow I would appreciate it.

Quick question for you. These files that you're copying, are they large files like videos or are they millions of small files? If it's a lot of really small files, those transfer speeds actually aren't unusual as for each file it has to adjust entries in the file table before copying the next file. If it's large files, then I'd say there's something wrong.

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Data Medics - Hard Drive, SSD, and RAID Data Recovery Service Company

@karljt, I would start by assessing the physical state of your drives. To this end I would examine their SMART reports with a tool such as CrystalDiskInfo.

Next I would run a read benchmark against the drives using a tool such as HD Tune. If the curve is actually a 1MB/s or 2MB/s flat line, then I would suspect that the drive may be running in PIO mode. Are any of the SATA ports configured for IDE or legacy/compatibility mode?

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A backup a day keeps DR away.

It varies, but there are some very large files so shouldn't the data transfer rate speed up when I am copying these files over?