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Does a scratch drive have to be separate to system drive if it is a SSD?


New Member
Hello everyone,

In the days of conventional spinning hard drives conventional wisdom always dictated that the scratch disk should be separate to the system disk containing Photoshop. But is this the same with SSD?

The limited research I've done suggests that it isn't necessary and that if I have a large enough SSD system drive (looking at 2TB) then that can function as the scratch disk. Is this correct?

Or should I go for an external, dedicated SSD as a scratch disk?

I'm buying a new iMac Pro so can't install a separate internal drive.

Many thanks!


This is my personal opinion. If you can afford another SSD as scratch disk, it is the best option. A cost effective way would be using a normal HDD as a secondary disk for scratch - noting that the seek times would be longer but not noticeable to most users on most applications.


Power User
Source: D Fosse

Generally, no. The consensus regarding SSDs seems to be that you get the best performance by having scratch on the system drive. In other words, just leave it at default configuration.

It was different with spinning drives, where the disk's read/write head couldn't be in more than one place at a time. Then it was also important to have contiguous, defragmented space. That's no longer a consideration.

Still, the main thing is to have the required gigabytes available. Especially with smart objects, scratch sizes can become huge, ten to a hundred times the file size. In any case, the new M.2 PCIe SSDs are so ridiculously fast that the scratch disk is no longer the bottleneck it used to be.

Of course, if you have a second M.2 port on your motherboard it can't hurt to use that for a scratch disk if you want to have it entirely out of the way.