In my BIOS, I've got a setting called "SATA Controller" that can select either IDE or RAID.
It's currently set to IDE.
What does this setting mean, and will bad things happen if I change it?
My motherboard is an Asus P5VD2-MX if that helps.
In this BIOS setting, "IDE" means separate disks attached to the main disk controller will each be shown as one separate disk to the operating system (for example as C: and D:).
Bad things will happen if you change controller mode from IDE to RAID. Backup your data first.
Bad things will probably happen if you change controller mode from IDE to RAID. Unless you first back up your data, then reconfigure BIOS, connect up appropriate drives to appropriate connectors, configure RAID, reinstall OS and restore data.
The spec and manualsays
"UltraDMA 133/100/66/33" means Parallel ATA (PATA) historically known as just "IDE".
So you have two controllers, each of which controls two SATA connectors. The main controller also controls two IDE connectors. Each of the IDE connectors supports up to two devices.
The BIOS description is "SATA controller mode: [IDE] or [RAID]":
My initial guess was that "IDE" refers to a pair of internal PATA (IDE) connector for the VIA 8237A controller and that "RAID" refers to a pair of internal SATA connectors for the same controller. In that case You could probably only be using one or the other pair of connectors at a time.
I now suspect that
ASUS'/Phoenix's choice of words to describe this in the BIOS is not as clear as it should be.
For some reason, no one has mentioned the obvious differences between IDE and RAID (AHCI). IDE is a software EMULATION mode that allows operating systems that don't natively support AHCI (Advanced Host Controller Interface) and SATA to still be able to detect and use your drives as if they were connected to an IDE controller.
This, of course, means that you lose the additional functionality provided by AHCI (RAID is AHCI-compatible), such as NCQ (native command queuing), hot-swapping, etc.
For maximum performance, you should always put your SATA controller in AHCI or RAID mode. Please note that you cannot easily make this change AFTER installing the operating system. It is best to enable it and then install the OS.
I think some simple definitions may help clarify things.
RAID - Redundant Array of Independent Disks. Basically, this is where you have two or more hard drives acting as one single hard drive. This is desirable in systems where the possibility of loosing data at any one instance is critical and/or where an overall better r/w speed is desirable. But just enabling RAID in the BIOS is only the first step to obtaining a true RAID system. You still need to do other things like "stripe" each drive (meaning format and loose whatever is on them) in order to properly configure a RAID system.
SATA - Serial ATA, or Serial Advanced Technology Attachment. SATA and PATA are both IDE interfaces only SATA is faster than PATA (which some people say is contrary to electronic theory since parallel connections should be faster). So if you only have one hard drive you might as well leave the BIOS alone and set it to IDE. But really, it doesn't matter. That is, unless/until you format/prepare your drive(s).
Now if you do want to get better performance from your hard drives, you probably should be looking at installing or updating better chipset drivers and/or adjusting your drive controller properties to allow DMA (Direct Memory Access). That's usually done for you in Windows. But I digress. Hopefully, that answers it.
Put simply, no you cannot change the bios setting once the OS is installed, or it will bluescreen on you. IDE mode on that particular board is for when you do not have more than one hard drive and have no need for Raid.
This setting must be set prior to installing the OS, its a decision you make before you install, I guess you can just say IDE is Non-Raid on that motherboard.
To clarify the answer from @RedGrittyBrick - changing the mode from IDE to RAID will very likely cause problems. The reason for this is simple - your OS expects a given driver to work with the installed hardware. When you change this BIOS setting the way the OS interprets the hardware changes and it very likely will result in a BSOD.
That being said there are certain interchangeable settings from the OS's perspective. As long as the drive is presented in the same fashion the OS does not care. When I first received my new laptop (a Dell E6420) I had an existing eSATA enclosure I wished to use with it. Even if you do blue screen your system a few times you should be able to restore access by resetting your settings to their current configuration.
It is theoretically possible to inject the correct drivers in the case of a blue screen on the BIOS change as well.. I never spent the time to get that to work however.