Data Centers

Quick Tip: Improve your SATA disk performance by converting from IDE to AHCI

In this Windows Quick Tip, Jack Wallen shows you how to improve the performance of a SATA hard drive using a Windows Registry tweak.

Most modern computers take advantage of the Serial Advanced Technology Attachment (SATA) hard drive interface. There are plenty of reasons why this is so, and most administrators know that IDE is no longer considered a standard for hard drives. What many administrators do not know, however, is that for maximum compatibility, most PCs are set up to use the older IDE interface. Because of this, when you install Microsoft Windows on a machine it may recognize only the BIOS IDE setting and enable IDE-only at the registry level. This can, in some cases, decrease the performance of the PC.

Fortunately, there is a way around this that isn't all that difficult, and it will not require you to reinstall Windows.

This blog post is also available in PDF format in a TechRepublic download.

First I want to make the usual disclaimer: You will be editing your registry and possibly changing your BIOS's settings. As there is always a risk when making changes to either of these, please make sure you know what you are doing before you attempt this and make sure you have a solid backup of your system (just in case). With that said, let's dig in.
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Edit the registry

Open up the Registry Editor by clicking Start | Run in Windows XP or by typing "regedit" in the Desktop search box in Windows Vista and 7, and then type or click regedit to open up the registry editor. When the registry editor is open, navigate to this key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci

Once there (Figure A), you will see the Start key, which is the key you need to edit.

Figure A

Before you start modifying your registry, you might want to make a backup copy of that registry — just in case.
Right-click the Start key and select Modify. When you do this, another new window will open (Figure B). This new window contains all the data for the Start key. What you want to edit is the Value Data. Most likely your Value will be set to "3." You want to change that to "0" (no quotes).

Figure B

Make sure you change nothing but the Value Data.

Once you have made that change, click OK. You can now close the Registry Editor.

Reboot and BIOS

The next step is to reboot your machine and then enter into the BIOS. Since every BIOS is different, all I will say is that you need to enable the AHCI setting in your BIOS. When this is complete, allow your machine to reboot and hopefully you will enjoy a boost in performance. I say "hopefully" because not every machine will see a marked improvement.

What about RAID?

If your machine happens to use RAID, you need to repeat the same steps with only minor changes. During the Registry Editor phase, you want to look for either:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStorV

or

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStor

Once you have located either of the above, make the same change you did for the Start key and reboot your machine. You will still need to make the change in the BIOS as well, before the change will actually work.

Final thoughts

Hopefully you will find this gives your machine a performance boost. If the gains are minimal (or nonexistent), then no harm no foul. If you are unsure if any gains were made, put your machine through a test that pushes disk I/O to the limits and see if the performance has improved.

About

Jack Wallen is an award-winning writer for TechRepublic and Linux.com. He’s an avid promoter of open source and the voice of The Android Expert. For more news about Jack Wallen, visit his website getjackd.net.

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