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[20120129] NetBSD vs. disk transfer speeds vs. BIOS settings
A few days ago, Brian Hoard made an interesting finding about performance of g4u, a NetBSD/i386-based disk cloning system. Citing from Brians mail:

``First, my problem was I had just replaced my motherboard on my custom build PC. Once I got Windows 7 64-bit loaded and everything working, I sat up to clone my system drive. The drive is a 500GB Seagate Barracude, SATA 2 drive. Cloning locally to an identical drive.

When booting into g4u, my transfer speeds were extremely slow. Normally, my 500 Gb clones take only about 90 minutes. But this was still working after over 6 hours. The g4u transfer speed was reporting only 1.5 Mb/sec.

I shut things down, and went into my system BIOS. I noticed that the SATA mode was set to "IDE Mode" for my drives. I changed this to "AHCI Mode" and continued to boot into g4u. This worked to fix the transfer speeds, and my clone finished normally. Getting 83 Mb/sec.

Once the drive was finished, I attempted to boot into Windows, but it would not boot. I had to change my BIOS back to "IDE Mode", then Windows behaved normally.

Upon researching this, I am now learning that you should enable AHCI Mode BEFORE installing Windows for it to work. Apparently, if Windows is not installed while using AHCI Mode, it disables the drivers for AHCI on the system drive. So if you later enable AHCI in your BIOS as I did, Windows will not have the driver loaded. I saw there is a fix on the Microsoft web site, but I haven't attempted to try it yet.

If someone else runs into a similar problem, hopefully this will help you.''

FWIW, g4u-2.5beta1 is based on NetBSD-current from January 2012, so checking your BIOS may help anyone seeing bad disk performance out there.
(Emphasizes in the text added by me)

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