PS CS4 Scratch File Info

ME
Posted By
Mirek_Elsner
Jan 2, 2009
Views
398
Replies
5
Status
Closed
Can somebody explain or recommend good resource to learn how scratch files work in CS4?

I’ve seen many articles and posts but they apparently weren’t written by people who actually know what they were talking about or were related to way old versions of Photoshop.

Here is what I am looking for:
– Scratch files seem to be created even in 64 bit Photoshop with plenty of unused memory, so they are apparently not regular swap/page files. What sort of data Photoshop CS4 writes to them and why isn’t this information kept in memory instead?

– Do scratch file writes/reads occur at the same time as operating system paging? Is there any practical reason not to put PS scratch disk and OS paging file on the same physical drive?

– Do scratch files benefit more from higher bandwidth or faster seek time?

– What is the typical ratio for Photoshop CS4 for reads and writes to scratch files?

Thanks 🙂

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CF
chris_farrell
Jan 2, 2009
Page file, image files, o/s, and scratch disk, I have found, should be on separate maintained drives ( not partitions on the same drive ) for optimal performance.

Regardless of how much RAM you have PS ( I use CS4 ) will write to a scratch disk so make sure it’s a fast one. I currently use raptor 10k’s for O/S, current projects and scratch and that works very well for my system along with 16gb Ram ( although a stick has recent failed, so I’m on 12gb with reduced speed )…Archives and back ups are on 7200RPM drives

The bottleneck will always be the scratch disk until SSD’s are affordable and fully supported by the O/S….we’re almost there with that one….this year should see major developments and support.
PB
Peter_Banks
Jan 2, 2009
If you allocate more Ram to PS CS4 you should have less need for the Scratch Disk unless your files are very large. If you also have an nVidia Graphics card you can make use of the GPU.
My large files use to take up to 9 hours to process on a Dual Core processor with Vita x64, 16Gb Ram and CS3. Now with CS4 and Vista x64 with a Quad Core processor they take 30 minutes with the GPU added to the mix.

Peter Banks
NZ.
wrote in message
Page file, image files, o/s, and scratch disk, I have found, should be on separate maintained drives ( not partitions on the same drive ) for optimal performance.

Regardless of how much RAM you have PS ( I use CS4 ) will write to a scratch disk so make sure it’s a fast one. I currently use raptor 10k’s for O/S, current projects and scratch and that works very well for my system along with 16gb Ram ( although a stick has recent failed, so I’m on 12gb with reduced speed )…Archives and back ups are on 7200RPM drives
The bottleneck will always be the scratch disk until SSD’s are affordable and fully supported by the O/S….we’re almost there with that one….this year should see major developments and support.
CF
chris_farrell
Jan 2, 2009
Peter, the files can go upto 8/10gb (with 40ish gb scratch file) but my system can cope with large files. CS4 x64 on Vista x64 has made a dramatic improvement to the speed…
ME
Mirek_Elsner
Jan 2, 2009
Thanks John,

The article helped. I’m still wondering if a RAID 0 made of ordinary SATA disks or a single SSD(s) would be a better fit for Photoshop scratch disk. They have different performance characteristics and the suitability apparently depends on how Photoshop accesses the scratch files. After reading the article I think Photoshop writes to these files in large blocks (one image copy per each history state) and reads them only if the user decides to use the history (history brush, reverting to an older state…). So I would speculate that using RAID 0 may be actually more effective than SSD disk that has bad write performance.

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