did you say scratch disc?!

Hi gusy,
Could please explain what a sctatch disc is and how much of it I need to work comfortably with LR and CS5.
Although I have what I think is a quite up-to-date PC (my own build:lol
*I7
*120GB SSD for OS
*8GB RAM
I have noticed that when I use a clone/healing tool in Lr it gets quite sluggish at times. Has it got anything to do with scratch disc. I have heard some people have a seperate hard drive assigned to be their scratch disc. How doeas it all work?
Much obliged for your help

Lightroom does not require a scratch disk so if you're experiencing noticeable lags during editing its more likely a driver issue. Have you updated your video drivers lately?

I keep my photos on separate drives, my applications on the OS drive, and Lightroom catalog on yet another drive. But that's very different from using a scratch disk.

A scratch disk is similar to the pagefile created by your OS; its used to temporarily hold operations that cannot be stored in system memory. If you look at your C; drive (assuming you haven't manually reassigned drives), when you start up Photoshop you will see a Photoshoptemp file created. That is used to store history states and file caches, and allow you to undo operations in PS. The idea of having the scratch disk located on a separate hard drive is so that Window's pagefile and Photoshop's temp file will not compete for the same disk space.

As was said, Lightroom doesn't have the same need for a scratch disk that Photoshop does.

But, I'm definitely a proponent of having at least one "data drive" outside of your system drive. A lot of peope go a lot further than I have on my 5-yr-old work station, so I'll just use my setup as a "minimum": my 1/2 TB "data drive" has current shoots/images I'm working on (plus my music ligrary) and then two important Lightroom resources: I have my LR catalog on it, which has both the metadata "stuff" and the Previews for all my catalog images. Then, I also keep the Camera Raw Cache, which holds 1:1 previews/Develop module previews for LR (as well as Photoshop Camera Raw if you have it installed).

By default, both these things are created in a directory that is likely on your system drive so you have to change them yourself. You change the Camera Raw cache location through Lightroom in the Edit/Preferences dialog and in the File Handling tab. There is also a size setting that is by default way to small for practical use -- I'd say a bare minimum of 5GB, but typically people set it quite a bit higher.

Your Catalog can be moved in different ways.

You also can designate a location for your catalog backups -- when the backup dialog pops up, you can click to choose a new location.

Have you got another hard-drive in there?
I wouldnt assign scratch disk in photoshop to your main SSD drive. Put it on another drive.

I keep all my photos on seperate drives (3) on a network, only th OS/programme files are on the C drive, then I have an empty 500gig drive installed just for Photoshop to use as a scratch disk.

siddr20 wrote in post #13048927
Have you got another hard-drive in there?
I wouldnt assign scratch disk in photoshop to your main SSD drive. Put it on another drive.

Yes, I have my OS on SSD and HDD for photos music and docs.
I followed your advice and moved the Scratch Disc to HDD. However, wouldn it be better to assign the faster drive for the scratch disc?

tommmy.star wrote in post #13055183
Yes, I have my OS on SSD and HDD for photos music and docs.
I followed your advice and moved the Scratch Disc to HDD. However, wouldn it be better to assign the faster drive for the scratch disc?

Well, I'd say that it would depand on the capacity of the SSD drive. I don't have any SSD drives, but I understand that they are relatively spendy, so people get smaller drives than your typical internal "data" disk drive.

It would be a good experiment -- run through some Photoshop processing using the SSD as the scratch drive and then the HDD, and see if one shows a significant speed advantage over the other. You'd have to design a test that made max use of the scratch disk and that would take some thought, understanding what made substantial use of the scratch disk and then developing PS actions that then you could call for multiple images.

I think you'll find this link helpful, It recommends putting the scratch disk on the SSD drive: Optimize performance Photoshop CS4, CS5

I personally think scratch disks are an anachronism that go back to when operating systems could not address large amounts of RAM. But with 64-bit operating systems and significant RAM installed (I have 8 GB) my scratch disk is rarely accessed unless I processing a large number of images.

I have my OS and programs on a RAID 0 drive, and a separate disk for Photoshop's scratch disk, Adobe Camera Raw/Lightroom cache. I can see the scratch disk store the original image but after that its rarely ever accessed. Perhaps I'm just not processing really large files.