Photoshop scratch disk

If you haven't read my other thread, I'm adding an extra internal hard drive to my computer that I'm having redone. I'm thinking about splitting it into 3 partitions, one to mirror my C drive, one for storage and one for scratch disk. Will a partition fore scratch disk work well and if so what size should the partition be? What do you guys think?

A scratch disk that's separate from your "C" drive will provide improved performance for Photoshop when doing large file reads or writes of information, because it allows the computer to access each drive at the same time and independantly of each other. So one drive is paying attention to the Windows instructions and application operation ... while the second drive only pays attention to the data it's reading or writing for your image. (I'm oversimplifying - but that demonstrates the concept.) When everything's run from the same drive, your computer is constantly moving its drive heads on your disk back-n-forth really fast to do everything at once. It may be reading a Windows instruction for a few milliseconds or running a background operation that requires disk data, then jumping to the location it's now writing that 40MB+ file you just created ... now back again for Windows ... then back to write file data ... etc. Although we're talking very short periods of time for the head to switch to different sectors on the disk and jump to and fro - it adds up when working with large files.

I don't have any performance numbers to toss at you, but you'll notice a substantial improvement when working with LARGE files. Not so much on little stuff. But be sure to buy the fastest addt'l drive you can such as 7500-10,000RPM and don't waste your time with 5,000RPM drives or USB attached disks. In other words: if it isn't using your drive cables INSIDE the computer and your built in bus speeds - you won't get noticeable improvements with a scratch disk in most cases.

Oh - I also wanted to note you mention mirroring your primary drive on 1 partition and using scratch disk in another partition ... but same drive. You'll end up with the same performance bottleneck doing that since every read/write the "C:" drive completes has to be duplicated on the mirror partition. So now it's just drive #2 that's trying to do all the operations at once and that'll eliminate the performance improvement you're seeking. Your scratch disk should be separate from any Windows drive, or Windows mirror. Sorry ...

You are asking one drive to do the work of three, performance will most likely take a dump. Hard drives are cheap these days. Add drives to each job. I have three drives in my bays. The "C" drive, a back up and a raptor assigned only as a scratch disk. I also have 2 500gb usb drives as storage drives.

vetkrazy wrote in post #5762833
You are asking one drive to do the work of three, performance will most likely take a dump. Hard drives are cheap these days. Add drives to each job. I have three drives in my bays. The "C" drive, a back up and a raptor assigned only as a scratch disk. I also have 2 500gb usb drives as storage drives.

I use the same setup. Helps offset the handicap of an older generation processor. I'm currently planning a new custom PC and I'll still maintain this arrangement- 3 drives, one for backup, one for scratch disk plus external drives for more backup.

Exactly, VetKrazy. Mirror two separate drives ... then use a 3rd as a scratch disk. Add externals for more storage as needed.