Scratch Disks and Time Machine - Photoshop error

[onlinechris140]

So I have Photoshop and it was moaning about Scratch Disks being full.  I have space on my TimeMachine disk so I selected this to use. Photoshop started working fine.

Now it's seemingly screwed up this disk. TimeMachine won't backup.

I've tried to restart etc it won't work.  Does anyone know what has happened? What is Photoshop doing when you select this option? Is there something I can delete to resolve this?

{Thread renamed by moderator}

[Sahil.Chawla]

Hi there,

Sorry to hear about this, could you please let us know the version of Photoshop and the macOS version you're working on?

Could you have a look at this article and see if it helps? https://helpx.adobe.com/in/photoshop/using/scratch-disks-preferences.html

You may try setting up a different drive as Scratch Disk in Photoshop and see how it goes.

Regards,
Sahil

[melissapiccone]

Don't use your time machine as a scratch disk. How much free space to you have on your hard drive?You want at least 25% at all times. For Photoshop you ideally want more free space. How full is your time machine? How large is your time machine drive compared to your hard drive?

[onlinechris140]

sahil.chawla 
"Sorry to hear about this, could you please let us know the version of Photoshop and the macOS version you're working on?"

21.1.2 & macOS 10.15.2

melissapiccone
"Don't use your time machine as a scratch disk"
I can't quite turn back time. Also, Photoshop simply advises it needs more temporary memory my external drive had free space. 

There's nothing to suggest it would corrupt my back up / time machine drive. (eg PS doesn't have a warning or popup)

"You want at least 25% at all times"

That's not always possible, this is why I have external SSDs

How full is your time machine? How large is your time machine drive compared to your hard drive?

The drive is 1TB and there was about 200GB free, my drive is 250

Thank you for the replies but the actual question was "how do I fix my timemachine drive?" after using it as a scratch disk.  It will no longer backup.

[Conrad C]

onlinechris140 said: “Now it's seemingly screwed up this disk. TimeMachine won't backup.”

Does it give a reason? If it does, that would help us troubleshoot it. Does it say it thinks it’s out of space?

With Photoshop quit, what does macOS say the available amount of free space is on the Time Machine drive?

One of the big problems with using a Time Machine drive as a Photoshop scratch disk is that both features are fundamentally about taking over available free space, so that can set them up for a conflict. For example, if you open a Photoshop file so large that you need a lot of scratch disk space (enough that you make Photoshop use the Time Machine drive as a scratch disk), Photoshop might pre-allocate the amount of space it’s going to need. Then, when Time Machine goes to make a backup, it might look at the current free space, reduced by the amount Photoshop has pre-allocated, and say “I don’t have the space to do this.” That’s just a theory because we don’t have more info about why Time Machine is not working.

In theory Time Machine should work fine if you exit Photoshop, because Photoshop is supposed to let go of its scratch disk space when it quits.

"You want at least 25% at all times"
onlinechris140 said: “That's not always possible, this is why I have external SSDs”

When my laptop is out of scratch space, what I do is take a spare external SSD that’s empty, plug it in, and assign that to be the scratch disk. This is a much better solution than plugging in a Time Machine drive, because Time Machine drives are often slow hard drives (it is best for a scratch disk to be fast), and because nothing was competing with Photoshop for the space on the empty external SSD.

In general I try to keep more than 100-150GB of free space on my system drive, and I always spec enough internal storage to make that happen. But when I recently worked on a very large Photoshop document, that wasn’t enough room. I plugged in my external SSD as a scratch drive and found out that particular large Photoshop document wanted to create a 500GB scratch file. In other words, the amount of space you need depends on the size of the Photoshop document, so in some cases you may be opening documents that need more scratch space than the 200GB you are trying to take away from Time Machine. Try to find an empty drive to use as dedicated scratch instead.

[onlinechris140]

I appreicate the advice of how to tackle this before the event, i've 100% taken this onboard for the future.

However, how do I repair my Time Machine?

Does it give a reason?
It doesn't, it jut says can't backup, it's quite vague.

If it does, that would help us troubleshoot it. Does it say it thinks it’s out of space?
It doesn't say, it just says it failed to back up - TimeMachine in general isn't verbose.  It doesn't mention no space.

With Photoshop quit, what does macOS say the available amount of free space is on the Time Machine drive?

200GB

What can I do? There's no options to fix it, there's no options to scan it, there's no options to really do anything apart from click "backup" and have this fail..

[Conrad C]

Because Time Machine is giving you so litttle information, I’m not sure what the problem is. But I’ve wrestled with Time Machine problems in the past. One way to check for problems is to hold down the Option key while clicking the Time Machine icon in the menu bar; that will change the Time Machine menu. When the menu drops, choose Verify Backups and see if that scan tells you anything. It might take a while.

Also, here are a couple of Apple’s Time Machine pages with troubleshooting advice:

If you can't back up or restore your Mac using Time Machine

Time Machine troubleshooting on Mac

Time Machine troubleshooting by Pondini — try Section C. Backup Failures

When a Time Machine volume is mounted, it is possible to scan it with the First Aid option in Disk Utility.