Question about photoshop

[kayumidome]

I read something about photoshop that said "if you are having PhotoShop speed problems, having a partitioned 'scratch disk' that only PhotoShop can touch can help tremendously" What is meant by that exactly? And how do I go about doing that?

[daamon]

Hi kayumidome,

A "partitioned scratch disk" is either an entirely seperate hard drive, or a part of the existing hard drive that has been partitioned to appear as a seperate drive.

To achieve this, you either install an additional hard drive or use software like Partition Magic (or similar) to create a partitioned drive.

[lordsmurf]

I read something about photoshop that said "if you are having PhotoShop speed problems, having a partitioned 'scratch disk' that only PhotoShop can touch can help tremendously" What is meant by that exactly? And how do I go about doing that?

Yeah, that tip is mostly myth. It's better to use a whole separate drive for Photoshop scratch, but it does NOT have to be "reserved" only for PS, it just needs to be a drive that does not have OS files or OS scratch on it.

For example, I use a drive on my ATA card drive for PS scratch, but the drive also holds a lot of temporary video files. Nothing on it is used for or by the OS.

[Raga]

And then again, having a separate partition on the same drive won't do you much good either. It needs to be on a physically separate volume to be of any joy to you. The speed advantage is gained from using two drives simultaneously. Better even, have many scratches on off-OS drives, one per drive.

[kayumidome]

What is a "scratch?"

[Raga]

1 : a mark or injury produced by scratching; also : a slight wound
5 a : a test of courage b : satisfactory condition, level, or performance <not up to scratch>
6 : a contestant whose name is withdrawn
7 : poultry feed (as mixed grains) scattered on the litter or ground especially to induce birds to exercise -- called also scratch feed
9 slang : MONEY, FUNDS
17 : a place where temporary files are stored

Pick your choice.

[Cornucopia]

taken from "scratch pad", a physical notepad that allows you to jot down temporary items quickly.

Scott

[SCDVD]

It would help to understand why a separate drive helps with Photoshop. To start with, Photoshop itself is a large application and occupies a lot of memory when it is loaded. On top of this, the image file that is loaded occupies even more memory. This is compounded by the fact that additional working copies of the image file are also resident in memory to be used for the editing that is underway, as well as undo and redo functions etc. The net result of all of this is that Photoshop is a memory hog. To cope with this, Windows sets up space on the hard disc that is called "virtual memory". It shuffles part of the content of memory on and off of the hard disc as required to make room for active processes in RAM memory. This allows the program to run and not crash from memory starvation but there is a significant price to pay; that is speed or performance. Disc storage access is much slower than RAM access. So the impact is much slower operation, which is obviously much better than not running at all. The most effective performance booster of all is to have plenty of RAM - at least a Gigabyte. Professional Photoshop users often use more. This minimizes the need for a lot of the disc swapping (virtual memory) to start with.

The reason that it is beneficial to have a separate hard disc for Photoshop is to prevent the disc accesses by Windows to its own operating files contending with Photoshop's disc accesses to its own files. The combination of plenty of RAM and a separate hard disc for Photoshop does performance magic for Photoshop.

[lordsmurf]

That is very true. I have a 1GB of RDRAM for example, and it is super fast compared to other systems with 512 or 256, even if those have faster CPUs.

[edDV]

All this relates directly to the size of the image you are working with and the number of clip buffers, undos, etc.

All of these add up to the total amount of real or virtual RAM you need.

Take a ~8 MegaPixel uncompressed image as an example.

3000x2000 uncompressed at 8bit x3 RGB = 3 bytes per pixel or ~18MB

make a composite of many clips with several layers of undo and you quickly get into virtual RAM.

Magazine quality scans may be 30-90MB per layer or more. That is why high end Photoshop workstations may have a dedicated RAID 0 for the scratch drive.
This used to be more common in the past (late 90's) than today since RAM is more affordable now. But it does help to explain the terminology.

[kayumidome]

Thank you Lord Smurf, edDv, SCDVD, daamon and Cornucopia. Your really helpful and informative.