What happens to disk cache with IDE RAID?

[zulch]

Does anyone know what happens to the disk cache (on disk) when using various RAID versions? I know with Adaptec RAID controllers (IDE included) they have a memory slot where you can put your own chip in - 4 to 64MB I believe. It's needed for RAID 5 to stay fast, not sure about others.
I'm asking specifically about the Promise RAID 0 that is found on many MB's. I don't remember seeing a memory slot on Promise controllers. It would be nice to be able to simply drop in an old stick of 32MB SDRAM for a hell of an upgrade.
Is the disks cache still used, is it in the controller... or does the OS handle it:confused: ? If the system handles it, (maybe as a swap file) is there a tweaking of a file that will improve performance - short of putting it on its own disk.

While on the subject... what kind of memory chip will work for Adaptec RAID controllers? Anything special about it?

[Diggrr]

As far as I know, the disk cache is on the ide harddrive, so it would work with raid as it would with any other setup. The controller's job is to split the info between the different disks.
I believe the controller cards have a cache because of the pci bus bandwidth limitations, allowing it to store incoming data while it's also writing to the drives.

[Patchmaster]

The cheap Promise RAID controllers provide the RAID function in the driver software; the controller has little if anything to do with it. That's why there are hacks out there that show how to turn a really cheap non-RAID Promise controller into a RAID controller by just rerouting a couple contacts and loading the RAID drivers.

Whatever cache is physically on the hard drive will remain in effect. Whatever software cache Windows provides will also remain in effect and probably be completely unaware of the RAID aspect.