35 Replies Latest reply: Jan 19, 2012 11:58 AM by LarryM01 RSS

    Photoshop CS4 does NOT use RAM as scratch disk

    LarryM01 Community Member

      Photoshop CS4 does NOT use RAM as scratch disk

      as far as I can tell.

       

      I have 20 GB RAM and still Photoshop uses the hard disk as scratch disk.

      (OS = Win 7 64).

       

      Can I force the use of RAM as scratch disk?

       

      /Larry

        • 1. Re: Photoshop CS4 does NOT use RAM as scratch disk
          Community Member

          Perfectly normal, expected behavior.

           

          Photoshop always uses a scratch disk, from the very instant you open an image file or create a new document.  Always.  No exceptions.

           

          See my reply to this other user's post:

           

          http://forums.adobe.com/message/4146851?tstart=0#4146851

           

           

          ____________

          Wo Tai Lao Le

          我太老了

          • 2. Re: Photoshop CS4 does NOT use RAM as scratch disk
            Community Member

            Hey, you're the "other" guy too!    You double posted.

            • 3. Re: Photoshop CS4 does NOT use RAM as scratch disk
              the_wine_snob Community Member

              The closest that you can get would be to create a RAM Disk, but think that, all things considered, you will be best off using a physical HDD, for Scratch Disks, and leaving your RAM for operations that do use RAM. That will allow for less use of Scratch Disks, and you might see an improvement, over having less RAM available. With fast and cheap (were cheaper, prior to the Taiwan floods) HDD's, RAM Disks are pretty much a thing of the past, or only really useful under certain circumstances.

               

              Good luck,

               

              Hunt

              • 4. Re: Photoshop CS4 does NOT use RAM as scratch disk
                Community Member

                I normally figure 30 to 50 times or more the size of your largest file ever for the minimum size of your main scratch disk.  My dedicated, physically separate main scratch disk drive is 200 GB in size.  In comparison, any RAM disk would be utterly insignificant.

                 

                 

                ____________

                Wo Tai Lao Le

                我太老了

                • 5. Re: Photoshop CS4 does NOT use RAM as scratch disk
                  Trevor.Dennis CommunityMVP

                  I've always bumped my scratch disk whenever updating my OS drive.  So I currently use a 150gb VelociRaptor that does nothing but PhotoShop scratch space - before that I used a 100Gb 7k2 drive for scratch, but that now sits on a shelf unused.  In fact the 150Gb v'raptore has survived two upgrades as I got a 300Gb VelociRaptor for OS the day Windows 7 was released.  That 300Gb v.raptor is now paired with a second one in a raid0 that has better sequential read/write times than my SSD OS drive.  This evolution approach is easy on the pocket, but you end up with a lot of different sized drives so you can't suddenly decide to raid them.

                  • 6. Re: Photoshop CS4 does NOT use RAM as scratch disk
                    the_wine_snob Community Member

                    Yes, I have 2x 500GB SATA II's, that sit for Scratch Disks, but they were set up, before retirement, when I did many high-rez triple-trucks and panos. Now, it's probably overkill for just my work, but have not bothered to change settings - besides, might do some big panos for myself?

                     

                    Hunt

                    • 7. Re: Photoshop CS4 does NOT use RAM as scratch disk
                      Noel Carboni Community Member

                      I think Larry is responding to Adobe's claim that Photoshop will use RAM above 4 GB as scratch space.  Trouble is, I think that is outdated info.  I don't recall where I saw that claim, but it's definitely out there somewhere.

                       

                      The thing is, Photoshop CS4 has a true 64 bit app in the package, so you'll want to use that variant, Larry, to take the best advantage of your large RAM.  You can safely set your Photoshop RAM limit to even as high as 95% with 20 GB on tap.

                       

                      -Noel

                      • 8. Re: Photoshop CS4 does NOT use RAM as scratch disk
                        D Fosse Community Member

                        I think the info still holds, but it was RAM used as a cache for the scratch disk.

                         

                        But of course that was only relevant for 32 bit Photoshop. With the 64 bit app it's moot.

                         

                        Either way, a scratch file is always created.

                        • 9. Re: Photoshop CS4 does NOT use RAM as scratch disk
                          Chris Cox Adobe Employee

                          >> But of course that was only relevant for 32 bit Photoshop. With the 64 bit app it's moot.

                           

                          Nope, same still applies.  Only difference is 64 bit can use more RAM.

                          • 10. Re: Photoshop CS4 does NOT use RAM as scratch disk
                            Chris Cox Adobe Employee

                            >> I think Larry is responding to Adobe's claim that Photoshop will use RAM above 4 GB as scratch space.  Trouble is, I think that is outdated info.

                             

                            Yes, that part is outdated for the 64 bit app.  It still holds for the 32 bit app.  And even with the OS caching, the sratch disk still gets used.

                            • 11. Re: Photoshop CS4 does NOT use RAM as scratch disk
                              LarryM01 Community Member

                              Thanks for all your comments. Sorry about the 'double' posting.

                               

                              Partition as scratch disk: Using a partition a fairly rapid SAS raid system.

                              But anyway I would like to have all scratch disking in RAM.

                              Because I think that should increase the performance.

                               

                              Might be a difference between RAM used by Photoshop and Scratch disk used by Photoshop in RAM? 

                               

                              I know I have set 70% of RAM (=13 GB) to be used by Photoshop. 

                              When it comes to Scratch disk you MUST set a Primary scratch disk on a hard drive. 

                              Could any other setting increase the use of RAM for scratch disk?

                               

                              The scratch disk on the hard drive seems always to be used.

                              Yes, it is possible that Photoshop caches and uses RAM for scratch disk,  and then just also double saves to the hard drive as a safety measure.  But why would Phshp vaste CPU energy to do that?

                               

                              So - how do you know that any or all scratch disk data is stored in RAM and not only on the hard disk? 

                              What's the proof that Phshp uses RAM as scratch disk?

                               

                              My main issue is that I want to use the RAM as much as possible.

                               

                              Am I?

                               

                              /Larry

                              • 12. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                PECourtejoie CommunityMVP

                                "Yes, it is possible that Photoshop caches and uses RAM for scratch disk,  and then just also double saves to the hard drive as a safety measure."

                                Photoshop does use the RAM as cache.

                                 

                                "But why would Photoshop vaste CPU energy to do that?"

                                Because the engineers tested it, and saw it gives the fastest results...

                                 

                                "What's the proof that Phshp uses RAM as scratch disk?"

                                The fact that you have the guy that wrote part of the code posting in the thread should be good enough...

                                But if you don't believe him, make a test: search for a relevant Photoshop speed test. (not one that just uses radial blur, but some like retouchartist or macperformance guide large, or medium)  Run it. Time it. 

                                Reduce the amount of RAM used by Photoshop in the preferences.Run the test, Time it.

                                Remove some RAM, Run the test, time it.

                                 

                                Or look at this: http://macperformanceguide.com/PhotoshopCS5-performance-vm.html

                                • 13. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                  PECourtejoie CommunityMVP

                                  If you want to have no paging on the hard drive, look for the maximum amount of memory you can install on your machine. Some use 16Gigs sticks, and up to 96Gigs of RAM (but I doubt that the speed bump would be worth the money invested.)

                                  • 14. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                    LarryM01 Community Member

                                    Hi PECourtejoie,

                                     

                                    thanks for your reply.

                                     

                                    I am very sorry but this just rises more questions:

                                     

                                    I don't see how testing the 'amount of RAM used by Photoshop' say anything about if scratch disking happens only on the hard disk OR in RAM and the hard disk.

                                    All you can see is that the hard disk is used as scratch disk.

                                    If you choose 1% of RAM to be used by Phshp, yes it goes slower than if you allocate 70%. But does it

                                    say anything about scratch disk in RAM? The same amount of data goes to the Primary scratch disk.

                                     

                                    And I don't see that  putting in *maximum* RAM memory into the machine  avoids having  paging on the hard drive (if that is your description of using Scratch disk on the hard drive?).

                                    In my case it would mean putting in 128 GB into the machine.

                                    So if I put 127 GB into my machine there would still be paging to the hard drive??

                                     

                                    You might mean that *much* RAM at some point stops paging to the hard disk?

                                    And if so, which amount of RAM would stop paging?

                                     

                                    You must forgive me for being a little stupid..

                                     

                                    /Larry

                                    • 15. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                      LarryM01 Community Member

                                      Hi Chris Cox,

                                       

                                      Photoshop 64 bit (CS4).

                                       

                                      If scratch disk data is cached into RAM (when you have it) does that mean that the discussion of speed for the scratch disk hard drive has no great point (since a reasonable if not all amount of the current data is anyway in RAM)?

                                       

                                      Does Photoshop on a machine only use the RAM that is 'set to be used by Photoshop'?

                                       

                                      Meaning that any caching of scratch disks happens within this allocated RAM.

                                      And meaning yes, the scratch disk data IS cached into this RAM?

                                       

                                      And that any RAM not allocated to be used by Photoshop is vasted for Photoshop?

                                       

                                      Meaning that you should allocate as much RAM as possible to Photoshop. But should you still avoid allocating 100%?

                                      What is the rule for allocating RAM to Phshp? It cannot be a percentage any more since the amount of RAM can vary.

                                      Is the rule to leave a certain amount RAM for other processes and allocate the rest??

                                       

                                      TIA

                                       

                                      /Larry

                                      • 16. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                        Noel Carboni Community Member

                                        Assuming you don't try to run several RAM hungry 64 bit apps simultaneously (i.e., when you're running Photoshop that's the one big app you're running) you can set Photoshop's RAM limit so as to leave just a gigabyte or so free for the OS.  With 16 GB of RAM I have my setting at 95% and never see problems.

                                         

                                        Thanks for clarifying, Chris.  I guess I just assume that anyone running a 64 bit OS would naturally be running the 64 bit build of Photoshop.

                                         

                                        Regarding Photoshop's scratch disk use, Larry, no matter HOW much RAM you have you want a fast scratch drive with hundreds of GB free.  That's practical experience talking.

                                         

                                        -Noel

                                        • 17. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                          PECourtejoie CommunityMVP

                                          "I don't see how testing the 'amount of RAM used by Photoshop' say anything about if scratch disking happens only on the hard disk OR in RAM and the hard disk.

                                          All you can see is that the hard disk is used as scratch disk."

                                          You would see when the hard disk is hit. If you could record an action with your common workflow, you would be able to see if everything fits into RAM.

                                          But I'm confused about the reason you are posting here: to understand how it works, or because hitting the hard disk brings unacceptable slowdowns in your workflow?

                                          • 18. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                            LarryM01 Community Member

                                            Thanks Noel,

                                             

                                            My Phshp 64 says in my Preferences- Performance:

                                            (It seems to have changed since I run some tests)

                                            Available RAM: 18485 MB

                                            Ideal Range: 10166-13309 MB.

                                            70% allocating gives 13 GB.

                                            I believe you when you say I can use 95% = 17,5 GB.

                                            Is this Ideal Range something that you don't have to care about?

                                             

                                            My Tempfile on the Primary Scratch disk very seldom exceeds 8 GB.

                                            Why should I have a hard drive Scratch Disk with hundreds of GB free?

                                             

                                            Seriously, I am trying to understand this.

                                             

                                            /Larry

                                            • 19. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                              D Fosse Community Member

                                              Under some circumstances a scratch file can really explode. I'd never use anything under 150 - 200GB.

                                               

                                              Most of the scratch activity is background anyway. You can hear the disk spin, but that doesn't mean it's slowing you down.

                                              • 20. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                LarryM01 Community Member

                                                Hi PECourtejoie,

                                                 

                                                I really try to understand this, please.

                                                 

                                                I don't know if 'Hitting the hard disk brings unacceptable slowdowns in my workflow'.

                                                Because I don't know what unacceptable slowdowns are.

                                                Any operation in Phshp takes time, and you always want it to go as fast as possible..

                                                 

                                                I know that if Phshp only worked against RAM instead of constantly saving to (and reading from) the hard drive it ought to go faster.

                                                But I still don't know if this is the case, because there is a constant use of a tempfile on the hard drive's Scratch disk!

                                                 

                                                So far I understand that Phshp may BOTH work in RAM AND save data to the hard drive Scratch disk.

                                                 

                                                It could be possible that the writing to the hard disk happens when Phshp is idle from other tasks and that the reading only happens when data has disappeared from the Cache in RAM.

                                                That could be a scenario where a Scratch disk on Hard drive doesn't  interfere with Phshps performance, and an explanation why we should not bother about the Scratch disk on the hard drive.

                                                But I would very much like to have some confirmation on this, IF this is the explanation of how the Scratch disk on a hard drive works without influencing Phshp's performance??

                                                 

                                                Everybody just seem to assume that Photoshop uses (some) parts of RAM as work space - I just need a better understanding of this. And some correct descriptions.

                                                 

                                                /Larry

                                                • 21. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                  Jeff Schewe Community Member

                                                  LarryM01 wrote:

                                                   

                                                  Everybody just seem to assume that Photoshop uses (some) parts of RAM as work space - I just need a better understanding of this. And some correct descriptions.

                                                   

                                                  Try reading this: Memory Allocation and Usage

                                                  While based on Photoshop CS2, as far as I can see, it's still accurate (right Chris?)

                                                  • 22. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                    Community Member

                                                    LarryM01,

                                                     

                                                    Not until—and unless—computers with several hundreds of GB of built-in RAM became feasible, economically viable and commonplace, would Adobe programmers would remotely entertain the notion of providing an option for the user to bypass the Photoshop scratch disk and use RAM only.

                                                     

                                                    You have had the nature of the compulsory and ever-present scratch disk explained to you in detail, including by notable luminaries like gurus Chris Cox and Jeff Schewe, and others with admirable and seemingly inexhaustible patience.

                                                     

                                                    At this point, you are only taking this discussion to absurd extremes and wasting everybody's time.

                                                     

                                                    Just face reality as stated in post #1 of this thread:

                                                     

                                                    Perfectly normal, expected behavior.

                                                     

                                                    Photoshop always uses a scratch disk, from the very instant you open an image file or create a new document.  Always.  No exceptions.

                                                     

                                                    End of story.

                                                     

                                                     

                                                    ____________

                                                    Wo Tai Lao Le

                                                    我太老了

                                                    • 23. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                      Community Member

                                                      A couple of additional  thoughts in parting:

                                                       

                                                      Photoshop moves stuff from the scratch disk to RAM and back all the time, as needed and as feasible.

                                                       

                                                      Additionally, if you think that nothing else is going on on your computer in regard to RAM and hard drive usage while working in Photoshop, just fire up the Activity Monitor and disabuse yourself of that misconception.

                                                       

                                                       

                                                      ____________

                                                      Wo Tai Lao Le

                                                      我太老了

                                                      • 24. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                        Noel Carboni Community Member

                                                        Ramon, you wrote:

                                                         

                                                        "Not until—and unless—computers with several hundreds of GB of built-in RAM became feasible, economically viable and commonplace, would Adobe programmers would remotely entertain the notion of providing an option for the user to bypass the Photoshop scratch disk and use RAM only."

                                                         

                                                        I don't mean to point out the obvious, but what happens when you just deconfigure all the scratch disks in the Edit - Preferences - Performance dialog, hm?

                                                         

                                                        -Noel

                                                        • 25. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                          Noel Carboni Community Member

                                                          Only you can determine how much RAM is needed for the other things you'll want running while using Photoshop.  The "ideal range" is just a loose guideline.  No OS itself is going to starve for RAM with 1+ GB available to it while PS is running.

                                                           

                                                          -Noel

                                                          • 26. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                            Noel Carboni Community Member

                                                            I'm not where I can test that right now with Photoshop CS5, but that's not how it used to work.  It used to be (last I looked carefully, which was way back) that it would not use scratch space at all if no drive was selected, and I haven't read anything that suggests otherwise...  I'd love to hear Chris' thoughts on this.

                                                             

                                                            -Noel

                                                            • 27. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                              pf22 Community Member

                                                              Noel Carboni wrote:

                                                               

                                                              I'm not where I can test that right now with Photoshop CS5, but that's not how it used to work.  It used to be (last I looked carefully, which was way back) that it would not use scratch space at all if no drive was selected, and I haven't read anything that suggests otherwise...  I'd love to hear Chris' thoughts on this.

                                                               

                                                              -Noel

                                                              I'm using CS5 on a Win7 Pro 64Bit system and you have to select a Scratch Disk.

                                                               

                                                              I currently have 5 drives in my system, 2x SSD's + 3x spinners, and on my system Photoshop defaulted to the C drive, the larger of my two SSD's, so I had to point it towards the second smaller SSD which I installed specifically for Photoshop.

                                                               

                                                              You can also select any, or all, of the drives in the system to be used as Scratch, and define the order in which they will be accessed. So for my system I have the SSD, plus a 1TB spinner, in that order, I've also given Photoshop access to 70% of the 16GB RAM I have installed; seems to be working fine!

                                                               

                                                              All the best

                                                              Paul

                                                              • 28. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                Noel Carboni Community Member

                                                                Thanks.  I'm on the road with an iPad and can't check Photoshop operation myself right now.  The last time I tried deconfiguring all the scratch disks entirely was back in PS 6 or 7 as best I can remember.  I did not realize that the configuration rules have changed.  Or maybe I just remembered wrongly.

                                                                 

                                                                Whatever the case I don't much appreciate being called derogatory names by a forum member who chooses to be abusive after having been banned once from this very forum.  Take your attitude elsewhere, Ramon Castaneda aka Tai Lao.  It is not wanted here.

                                                                 

                                                                -Noel

                                                                • 29. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                  Community Member

                                                                  pf22 wrote:

                                                                   

                                                                  Noel Carboni wrote:

                                                                   

                                                                  I'm not where I can test that right now with Photoshop CS5, but that's not how it used to work.  It used to be (last I looked carefully, which was way back) that it would not use scratch space at all if no drive was selected…

                                                                   

                                                                  That is completely absurd and irrational.

                                                                   

                                                                  Photoshop will even return an error message and refuse to launch if the designated scratch disk is disconnected or otherwise not found.  If you do not explicitly designate a scratch disk volume, Photoshop's scratch disk file will transparently default to your boot volume, even if you don't see that inexorable fact reflected in your preferences.

                                                                   

                                                                  The above quote in pf22's post is all I see of N. Carboni's post, as I have now re-activated Greasemonkey and the afplonk! script, which had been temporarily and inadvertently disabled in Firefox.

                                                                   

                                                                  ____________

                                                                  Wo Tai Lao Le

                                                                  我太老了


                                                                  • 30. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                    Community Member

                                                                    Photoshop always uses a scratch disk, from the very instant you open an image file or create a new document.  Always.  No exceptions.

                                                                    • 31. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                      Community Member

                                                                      A post of mine has been deleted from this thread—presumably by a bored forum bouncer with little else to do—which had been my reply to a comment by another poster to this effect:

                                                                      "I don't mean to point out the obvious, but what happens when you just deconfigure all the scratch disks in the Edit - Preferences - Performance dialog, hm?"

                                                                      The thrust of my deleted response was:

                                                                      Then Photoshop's scratch disk file defaults to your boot drive.  Oy!

                                                                       

                                                                      After that, I reactivated Greasemonkey and afplonk! and plonked the…user in question…again.

                                                                       

                                                                      It has never, ever been possible to prevent any version of Photoshop whatsoever from creating or using a scratch disk for every open document.  Any pretense to the contrary is a fallacy.

                                                                       

                                                                       

                                                                      ____________

                                                                      Wo Tai Lao Le

                                                                      我太老了

                                                                      • 32. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                        LarryM01 Community Member

                                                                        Thanks Jeff Schewe,

                                                                         

                                                                        "Try reading this: Memory Allocation and Usage"

                                                                         

                                                                        A beautiful description!

                                                                         

                                                                        Just what I needed.

                                                                        Written for CS2 but I assume it is still accurate.

                                                                        I have no further questions.

                                                                         

                                                                        (And I apologize for the provocative title on this thread).

                                                                         

                                                                        /Larry

                                                                        • 33. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                          Noel Carboni Community Member

                                                                          I apologize if I remembered wrongly about an ability to deconfigure the use of scratch drives.

                                                                           

                                                                          Ramon seems inordinately proud of his inability to interact politely with people on a public forum (and of employing special software to keep him away from others he doesn't know how to get along with), but I'm happy to be out of his sights.

                                                                           

                                                                          -Noel

                                                                          • 34. Re: Photoshop CS4 does NOT use RAM as scratch disk
                                                                            LarryM01 Community Member

                                                                            Hi Noel,

                                                                             

                                                                            it's cool.

                                                                            At least I knew that you now can not deactivate the Scratch disk on hard drive (I tried that :-)).

                                                                             

                                                                            My main issue in this thread was whether Phshp used RAM since it obviously all the time writes to the hard drive Scratch disk.

                                                                            In the CS2-link (Memory Allocation and Usage) it is clearly described as:

                                                                            "Data that previously was written directly to the hard disk by Photoshop, is now cached in this high RAM before being written to the hard disk by the operating system. ".

                                                                             

                                                                            So I am content.

                                                                             

                                                                            (I like this detailed CS2-description a little bit better then the also existing CS4/CS5 Memory Performance descriptions. For instance mentioning the use of Scratch Disk information on the Document..).

                                                                             

                                                                            /Larry