Parallel-ATA

Many tweakers forget one thing when they move their paging files to the second hard disk - only one PATA (Parallel-ATA) device can be active at any one time on the same IDE channel.

Most users slave the second hard disk to the first hard disk on the primary IDE channel and put the removable media drives (CD writers, DVD-ROM, etc.) on the secondary IDE channel. That is theoretically sound practice but it actually negates the purpose of moving the paging file off the primary hard disk!

Because both hard disks are on the same IDE channel, they can't be active at the same time. So, there is no way data can be read from both hard disks at the same time. In fact, because the secondary hard disk is often slower and smaller than the primary hard disk, the performance of the paging file on the second hard disk will actually be worse off.

So How Do We Make It Work?

The only way for this method to work is to put the first and second hard disks on separate IDE channels. That means the first hard disk gets hooked up to the primary IDE channel and second hard disk gets the secondary IDE channel. This allows both IDE channels can be active at the same time, delivering data from both hard disks concurrently.

In addition, the second hard disk needs to be at least half as fast as the primary hard disk. This allows the paging file on the second hard disk to be at least as fast as a paging file on the first hard disk. Otherwise, the performance advantage accessing the paging file concurrently on a second hard disk will be negated by the slower performance of the second hard disk.

Remember, if the first hard disk can serve data to and from both the application in use and the paging file faster than the second hard disk can access the paging file alone, then it is pointless to maintain a paging file on the second hard disk.

But if the second hard disk is more than half as fast as the first hard disk, then it would be advantageous to move the paging file there because the paging file can then be accessed concurrently with data on the first hard disk. In addition, the valuable outer tracks on the first hard disk will be freed up for use by the operating system.