Is my scratch disk working?

[Paul-ny]

I'm working on some big files, but I have an even bigger scratch disk set up, and I'm wondering whether it's working because I have been gettiing "can not complete operation because of insufficient RAM " warnings.   The scratch disk is a new SSD (ExtremePro Sandisk) 1TB, which I formatted to APFS and there's absolutely nothing on it. When in use, should Finder show me any files created by Photoshop on that disk? I don't see any, and whether Photoshop is running or not, Finder info on the SSD says Available Space is 999,75G and Used is about 1 MB.

 Photoshop Settings say this SSD is the primary scratch disk and it's active, could that be right? I can set my computer to see invisibles and that shows a temp folder on the SSD but I don't know enough to get around the permissions denial for looking inside it.

[melissapiccone]

How much actual RAM do you have? A scratch disk won't make up for lack of real RAM.

[Paul-ny]

I have 29 GB available and Photoshop settings allowing use of 20GB, but I'm not really asking because of problems with inadequate RAM. I had slow behavior and this "insufficient RAM" warning only one time., and rebooting made that stop. But with a 1 TB scratch disk available I've been wondering whether the SSD is actually functioning as a scratch disk-- isn't that what a scratch disk is for, to stand in for the computer's RAM?  So now I really want to know if there is a way to tell whether the SSD is functioning correctly as a scratch disk or not. Photoshop Settings show it as the primary scratch disk, and as active. This SSD tends to stay very hot, even when Photoshop isn't running, and even when the laptop it's connected to has been sleeping for ten hours. Is that normal?

[melissapiccone · Accepted solution]

"isn't that what a scratch disk is for, to stand in for the computer's RAM? "

No... 

I think you have a misunderstanding of how a scratch disk is used:

A scratch disk is a hard disk drive or SSD used for temporary storage while Photoshop is running. Photoshop uses this space to store portions of your documents and their history panel states that don’t fit in the memory or RAM of your machine. By default, Photoshop uses the hard drive on which the operating system is installed as the primary scratch disk. 

Here is the full page:

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

Your insufficient RAM warning went away because rebooting freed up all of the RAM on your system allowing it to be re-allocated when you resumed your task. If your files are huge you might really not have enough RAM. 

[Paul-ny]

Thanks for the clarification. At this point it’s curiosity and not a computer problem that makes me want to know whether a scratch disk will show signs of being used; this is really why I posted.

There’s nothing on my external SSD to indicate it’s being used or has been used for anythiing at all: is this to be expected on an assigned scratch disk? Wouldn’t Photoshop create a folder for this storage? Would Finder set to Show Invisibles (command-shift-period) reveal such a folder? If it exists, does it get erased when not in use? Or is it totally invisible and I should assume my SSD scratch disk is fine?

[melissapiccone]

The SSD being hot is another issue - I have an external SSD that runs very hot. I don't think it's hot while my computer is sleeping but there is always background activity going on with Dropbox and my Backblaze backups. My computer fan is always going in addition to the SSD - very annoying when trying to make training videos. Try turning off all of the background tasks and see if it still runs hot while sleeping. 

[melissapiccone]

All great questions and I don't have any answers for you. I have never seen a folder or files created from PS on a Scratch disk but I've never gone looking for them, either. I would assume that nothing is written permanantly or it's immediately erased but again, I have no idea how it works. 

[simonp16574977]

Hi, I think I had the same problem as you. I needed to format my external drive to MacOS Extended Journaled then Photoshop recognised the correct free space.

[Shangara Singh]

 Photoshop Settings say this SSD is the primary scratch disk and it's active, could that be right? 

By @Paul-ny

You understanding is fine. Photoshop uses the scratch disks you specify in Prefs when it can (you can choose to see SD info in the status bar of the documents), either when idle, or when RAM isn't available. The scratch disk is cleared once you close a document or Photoshop. More info here:

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

My primary scratch disk is SSD, a partitioned main disk and formatted as APFS. When I open a file too big for RAM, I see the size going down almost immediately in a Finder window. Closing document doesn't clear scratch space (I would say that's a bug). However, closing Photoshop restores the space. Like you, I cannot see where files are being stored, even with show invisibles enabled.

Open a large file. Increase it's size to something way beyond what your RAM can handle and watch scratch disk in a Finder window. Does the size go down in the Finder window? It does here.

HTH.