Photoshop & USB scratch disk on an iMac

[dmdigital]

There's got to be some knowledgeable Mac/Photoshop guru's out there!

I now have my nice new iMac and was going to configure a USB 2.0 WD My Book drive as a scratch disk for Photoshop. Only one catch the drive doesn't appear in Photoshop's list of available devices (under Preferences>Performance). Can anyone tell me if this is possible, I know the drive is there as the Mac lets me do everything to it and it shows a USB drive icon on the desktop.

On my Windows systems it can be used as a scratch disk in this manner. Is this a Mac thing:confused:

[incisor]

There's got to be some knowledgeable Mac/Photoshop guru's out there!

I now have my nice new iMac and was going to configure a USB 2.0 WD My Book drive as a scratch disk for Photoshop. Only one catch the drive doesn't appear in Photoshop's list of available devices (under Preferences>Performance). Can anyone tell me if this is possible, I know the drive is there as the Mac lets me do everything to it and it shows a USB drive icon on the desktop.

On my Windows systems it can be used as a scratch disk in this manner. Is this a Mac thing:confused:

not really needed buit if you were going to use anything for a scratch i would suggest you use firewire... much better.

btw WD external drives have known problems with many macs and pc's for that matter...

[dmdigital]

Thanks Inc, the Firewire800 would definitely be better, just happen to have to WD drives. Haven't had any issues with either drive to date. What would you recommend for the Mac - Seagate, Lacie or something else??

Scratch disk allows temporary file data to be written rather than paged, speed is less of an issue than capacity. I have already found the Mac is very good, I tried the following edit last night (this killed my PC and my Laptop under Windows): 50 x 15.4MB RAW images, photomerged to a Panorama in Photoshop CS3 - 25 minutes! On the PC I had to save all as JPEG's and also reduce the size before I could get it to work and even then it took over 3 hours. This is a low resolution of what it looks like (click for bigger):

Nhulunbuy from town lookout
https://www.aulro.com/afvb/images/imported/2008/05/269.jpg (http://farm3.static.flickr.com/2325/2097540688_535ff27349_o.jpg)

[coedman]

Have you packed it out with ram? It seems to make a much bigger difference to a Mac than a Windows system...

[dmdigital]

Have you packed it out with ram? It seems to make a much bigger difference to a Mac than a Windows system...

3.06GHz with 6MB L2 cache, 4GB RAM, 750GB HDD. PS is set to use just over 2GB RAM for temp storage.

I'm inclined to agree with Inc's comment after a bit more experimenting, scratch disk is not really need

[disco2hse]

3.06GHz with 6MB L2 cache, 4GB RAM, 750GB HDD. PS is set to use just over 2GB RAM for temp storage.

I'm inclined to agree with Inc's comment after a bit more experimenting, scratch disk is not really need

With that amount of RAM and HD volume you don't want to use an external drive for your scratch disk. It won't see the USB flash drive because Photoshop will not recognise the flash drive driver as an acceptable scratch volume format.

If you are going to use Photoshop frequently (daily) create a partition on your HD for it. Otherwise letting Photoshop utilise its own scratch disk on the boot volume is more than adequate.

If you are going to be doing large image manipulation (most files larger than 50-75Mb) then you can consider getting a second HD (SATA + USB2.0, rather than Firewire + ATA) and use that for your scratch (they are cheap, cheap, cheap).

The easy way to think about it is the scratch volume IIRC needs to be three times the image size, for each image that is open.

Alan