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Fierce-hairdo
Participant
May 11, 2018
Question

If I have 128GB RAM do I need a separate Scratch Disk?

  • May 11, 2018
  • 1 reply
  • 1948 views

About to buy a new iMac Pro. Choice between 128 GB RAM and internal 1TB SSD that would be also be the scratch disk or 64GB RAM and 2TB internal SSD that I would partition so 1TB would be a scratch disk. Which is the best option?

Also, is it still preferable for the scratch disk to be separate from the drive the software is on when it is a SSD? I'm guessing not?

Other relevant info: I'd also being using the Mac for 3D software such a Modo and Z Brush. The iMac will be an 8 Core.

Many thanks!

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    1 reply

    D Fosse
    Community Expert
    D FosseCommunity Expert
    Community Expert
    May 11, 2018

    For "normal" use, the 128 / 1TB option will be fine - but it depends on how big your files are. For big files with smart objects etc, the required scratch space can easily go into several hundred GB. If you run out of disk space then, Photoshop will simply close down.

    There will always be a scratch file on disk, no matter how much RAM you have. Contrary to popular belief, it's not a simple "overflow"-situation, it's more complex than that. Think of scratch disk as main memory, and RAM as a fast-access cache.

    Don't partition. The best performance with SSDs is to leave everything on the system drive - system, scratch, programs, everything except image files.

      F
      Fierce-hairdoAuthor
      Participant
      May 11, 2018

      Many thanks D Fosse.

      My usage will be very intensive - very large files, sometimes upwards of 20GBs, many layers, smart objects etc. Would an external SSD scratch disk be as effective as an internal one?

      D Fosse
      Community Expert
      D FosseCommunity Expert
      Community Expert
      May 11, 2018

      It works if it's fast enough. But the ideal scratch disk is an internal PCIe SSD.

      With the file sizes you describe I actually think I'd go for the 64GB / 2TB solution. Again, don't partition. Just put scratch on the system drive. I think you should be prepared for scratch sizes in excess of 500GB.

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