External drive not appeared as scratch disk in Photoshop

[joyciHF]

Hello,

Before I did a clean installed of the mac into Monterey OS, I had a 4TB external HD in Mac extended journal format, which worked as a scratch disk in photoshop and illustrator CC. The external HD also acts as my time machine backup drive. 

Recently due to some problems in my mac that couldn't be solved, I formated the mac internal HD into APFS and did a clean installed of Monterey OS. The 4TB external HD (Mac extended journal) didn't show up in photoshop as a scratch disk. But my other 1 TB external HD (Mac extended journal) showed up. 

In illustrator, both the 4TB and 1TB external HD showed up as scratched disk in the primary and secondary scraatch disks, but when I tried to choose either external HD as scratch disks, it showed me a yellow triangle symbol with an exclamation mark. After restarted illustrator, it didn't make any changes to the scratch disk selection. 

Thanks. 

Photoshop and illustrator can't choose either external HD as scratch disk, does this have anything to do with the formats of the mac and the external HDs? 

[Kevin Stohlmeyer]

Hi @joyciHF Mac OS is getting harder to please these days. I would reformat your external 4TB drive to Mac OS Journal Extended again and see if it mounts properly. The other consideration is two fold:

1. Is your external drive an SSD? If its an older spin disk it may not work.

2. How is your external drive connected? USB-A or Thunderbolt 1 won't work due to speed limitations, it needs to be USB-C or Thunderbolt 3/4.

[joyciHF]

Hello Kevin,

Thanks for the advice. My external drive is HD (I think it's the older spin disk), not SSD. It's connected by a USB-A cable.

Does using a USB-C adapter help?

[Kevin Stohlmeyer]

Hi @joyciHF no you cant fake it - it needs to be a true USB-C port on both ends. USB-A is significantly slower with read/write speeds needed to effectively use it as a scratch disk.

[Kevin Stohlmeyer]

@joyciHF The other question is how much free HD space do you have on the external? Normally I like to keep my Time Machine completely separate from any other inputs. Running it on your scratch disk is a recipe for eventual disaster. I would never mix/risk that just for Scratch Disk.

[joyciHF]

@Kevin Stohlmeyer I see. The 4TB HD external drive has 2/3 free space left.

[TheDigitalDog]

Try running Disk First Aid (part of Disk Utilities); any better? 

[joyciHF]

@TheDigitalDog Thank you for the advice. I ran Disk First Aid for both the external hard drive and my mac's hard drive, and rebooted the mac, it still doesn't work. 

[TheDigitalDog]

So this drive is partitioned, right? It seems it has to be as if you have a scratch disk + Time Machine.

You might just have to back up anything you don't want to lose, reformat and partition again. 

Not an Illustrator user, but does it really need a scratch disk? PS sure, I can see that but Illustrator? 

[joyciHF]

Thanks for the advice. The external drive not partitioned. The Time Machine created a folder for itself, and I just use the rest of the disk for storage and for scratch disk. 

I think sometimes Illustrator needs to open a file that has a lot of images in there, it runs very slow, so I prefer to add a scratch disk. 

[Nancy OShea]

does this have anything to do with the formats of the mac and the external HDs? 

By @joyciHF

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Possibly.

Best Format for Mac External HD.

https://recoverit.wondershare.com/format-harddrive/best-format-for-external-hard-drive-mac.html

From Photoshop Help  - Set-up Scratch Disks

Supported drive formats for scratch disks

macOS: APFS or macOS Extended (Journaled)

Windows: NTFS, exFAT, FAT32

Drives not recommended for scratch disk

• Thumb drives
• Any USB-2 drive
• NTFS formatted drives on macOS