Scratch disk

[Redhartotter]

I have just upgraded PS to the latest version and now I only have one scratch disk. How do I assign another one? I had two in the previous version. Holding down command/option when I start up does not help.  Using Mac Sequoia 15.2

[Chuck Uebele]

You can set up scratch disk in your preferences: cmd-k, under the scratch disk tab.

[Redhartotter]

Thanks Chuck but this is what I get.........

Only one scratch disk available - how doo a assign another?

[Conrad_C · Accepted solution]

The uploaded image looks like a recipe, which probably wasn’t intended. But, we probably can guess what you were looking at, the Scratch Disk preferences with only one volume listed. If that happens, these are the questions you want to ask about the volume you want to use as a scratch disk:

• Is the volume a hard drive or SSD, and it’s connected internally or as external direct attached storage (DAS), such as USB 3 or Thunderbolt? Those should work. (Photoshop does not allow certain types of volumes to be scratch disks, for example you can’t use a removable cartridge or an NAS.) 
• Is the volume formatted as APFS or macOS Extended (Journaled)? (Photoshop won’t accept other formats as scratch disks.) 

If a volume doesn’t meet both of those requirements, it isn’t going to show up in the Scratch Disks list.

For more details about the requirements, read the later part of this Adobe help article:

https://helpx.adobe.com/photoshop/using/scratch-disks-preferences.html

[Redhartotter]

Ha ha! It is a nice recipe!!!

This is the volume I want to use. I have used these external hard drives as scratch disks before….

[Redhartotter · Accepted solution]

Here's the HD volume.  Formatted ExFAT.  I have never formatted a HD and they work fine...

[D Fosse · Accepted solution]

exFAT doesn't work well (or at all) on newer MacOS versions.

You need to reformat to APFS. That will obviously wipe the drive, so if there's anything you want to keep you need to find somewhere to park it.

[Redhartotter · Accepted solution]

Thanks.  I can do that.

[Conrad_C]

Here's the HD volume.  Formatted ExFAT.  I have never formatted a HD and they work fine...

By @Redhartotter

I can‘t explain why they worked before without reformatting, but ExFAT is definitely not on the list of supported formats in the Adobe help article I linked to earlier. Maybe they changed something?

One of the goals of a scratch disk is to help RAM, so a scratch disk should be as close to the speed of RAM as possible, which means as fast as possible. One issue with ExFAT is that for an SSD, I’ve seen tests that showed macOS is not as fast with ExFAT as it is with APFS. Maybe that’s one reason Adobe recommends APFS.

[D Fosse · Accepted solution]

exFAT was originally proposed as a cross-platform file system, so that you could swap disks between systems. That was its main purpose.

Unfortunately, it never worked well on either platform. It's unreliable on Windows, and more or less unsupported on Mac. Out of the box many external drives are still exFAT-formatted, but personally (on Windows), I reformat to NTFS first thing.

[Redhartotter]

Thanks. 

[Redhartotter]

Thanks. I will reformat.

[Redhartotter]

I haven't done this before.  I have attached  screen shots of the options I get:

One for APFS and one for macOS Extended.

Which one should I choose?      

[Conrad_C · Accepted solution]

According to the Adobe help article I linked to earlier, Photoshop will accept either APFS or macOS Extended for a scratch disk.

Between those, you can choose based on the type of volume. If the volume is an SSD (solid state drive), for performance reasons the newer APFS format is preferable. If it’s an HDD (hard disk drive), the older macOS Extended format might work better.

[Redhartotter]

It is an SSD.  Thank you so much for your patience and advice.  Much appreacaited.

Heather

[Redhartotter]

One more thing: should I choose the options 'Case Sensitive' and 'Encrypted'?

[Conrad_C · Accepted solution]

For a scratch disk, don’t choose Case Sensitive or Encrypted.

Adobe applications don’t work with case sensitive volumes:

https://helpx.adobe.com/creative-suite/kb/error-case-sensitive-drives-supported.html

Encryption isn’t needed on a scratch disk, and it might slow it down.

On a volume you use for normal everyday computing, encryption is recommended if you need to protect others from accessing personal data on that drive if it’s lost or stolen. I use encryption on internal and external volumes that store my files. But don’t use encryption for a scratch disk, which will contain only temporary, expendable files.

[Redhartotter · Accepted solution]

Thank you.  All good to go now.