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  • ramdisk

    Hi all,

    I have been playing around with ramdisks and i wanted to know the thoughts of people who may have done the same. I have used the free 1 avaliable from "http://www.mydigitallife.info/2007/05/27/free-ramdisk-for-windows-vista-xp-2000-and-2003-server/"

    I just wanted to know if their are any implications for using a ram disk. So far i have placed my page file, windows temp files and firefox cache on it. So far i have noticed dramatic improvments to my systems responsiviness. It makes me want to go our and get 8gb of ram and use 4 for the ramdisk. I cant believe that i just discovered ramdisks after all these years.

    The only issue i have noticed is that the load times on pr have increased.... cant figure that one out???

    Cheers

    Matt
    |TG-Irr| Aus-trooper

  • #2
    Re: ramdisk

    If a RAM disk gives you better performance, that means the caching strategy of the operating system sucks.

    There are exceptions, and temp files is one, as long as they aren't needed for recovery after a system power outage. For example, my mail server recommends using temp files for inter-process communication between sendmail and the spam/virus scanners. They don't need to write the files, and if the system crashes in the middle of the operation, no data is lost. (The sender will never be told the mail was accepted until the scans complete and the mail gets to the mailbox, so the sender will just retry later.)

    Putting a pagefile in RAM doesn't make sense. That's where stuff is supposed to go when you run out of RAM. So you're just forcing it to get used even earlier.

    Putting the FF cache in RAM means it gets wiped on reboots, so page loads will be slower after a reboot.
    Dude, seriously, WHAT handkerchief?

    snooggums' density principal: "The more dense a population, the more dense a population."

    Iliana: "You're a great friend but if we're ever chased by zombies I'm tripping you."

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    • #3
      Re: ramdisk

      Originally posted by ScratchMonkey View Post
      Putting a pagefile in RAM doesn't make sense. That's where stuff is supposed to go when you run out of RAM. So you're just forcing it to get used even earlier.
      Im not sure about that, ram is much faster than a hd, if u can spare it, when the pc does use the pf it will run faster?
      |TG-Irr| Aus-trooper

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      • #4
        Re: ramdisk

        But if the pagefile is only supposed to be used when RAM is exhausted, putting it in RAM means you have less RAM and will run out sooner, so the system will swap to the pagefile (now in another part of RAM) instead of leaving the data where it was.
        Dude, seriously, WHAT handkerchief?

        snooggums' density principal: "The more dense a population, the more dense a population."

        Iliana: "You're a great friend but if we're ever chased by zombies I'm tripping you."

        Comment


        • #5
          Re: ramdisk

          Originally posted by ScratchMonkey View Post
          But if the pagefile is only supposed to be used when RAM is exhausted, putting it in RAM means you have less RAM and will run out sooner, so the system will swap to the pagefile (now in another part of RAM) instead of leaving the data where it was.
          Not necessarily true that the pagefile is only for when RAM is exhausted. In Windows(general OS design actually) the pagefile is preferred for all instance data other than the currently active application(and even then...). This is why you can see pagefiles of many gigs while your ram is only half used. RAM is necessary for quick data push so if your RAM is full when windows needs to use it(because you don't have a pagefile, or a pagefile too small, etc) then windows has to do swapping and clean up at the time the data is needed causing significant slowdown. That's where the pagefile comes in, all data is preferred to go to the pagefile unless it is needed so that when the RAM is needed it's not full.

          The slowdown on loading pr might be because the game needs to load more data then is left in your pagefile and as such it needs to swap more things around instead of just moving it from one place on the hard drive to another? The slowdown then might be because the pagefile is of a fixed sized instead of anything necessarily wrong with the ramdisk? I'm really not sure here.

          Comment


          • #6
            Re: ramdisk

            What would cause the system to load "instance data other than the currently active application"? Presumably only the active app can load data, since other apps are waiting for data to hit RAM or on the run queue.

            Now I can see copying RAM to disk for when the page might be needed by another app, but you don't want to use other system RAM for that, because you're just speeding up the point at which you have to page.

            Admittedly a solid state disk separate from system RAM is another beast entirely. But when I hear "RAM disk", I assume a software emulation of a disk using system RAM.
            Dude, seriously, WHAT handkerchief?

            snooggums' density principal: "The more dense a population, the more dense a population."

            Iliana: "You're a great friend but if we're ever chased by zombies I'm tripping you."

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            • #7
              Re: ramdisk

              Why not just set your pagefile at 0?

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              • #8
                Re: ramdisk

                ram disks have been used for a long time now. If you have heaps of ram to spare then go for it. It is good for some applications where you can run them purely from a ram disk and they do start faster but one thing you will notice is that ram disks have more of a tendency to freak out with a lot of file transfers.


                - -

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                • #9
                  Re: ramdisk

                  Originally posted by sordavie View Post
                  Why not just set your pagefile at 0?
                  If you don't care about your data, that works fine. But if you want to be able to save your work when you run out of RAM, the pagefile lets the computer hobble along with too much stuff to fit, by simulating having more memory than you actually do.

                  There's also the case where you have a whole lot of idle apps "running" (blocked for some infrequent event). They can sit in the pagefile without affecting what you're currently working on, and will get swapped in when the event eventually happens.

                  Apps are not paged in their entirety, but in quanta of pages, typically 4k bytes. The code in a scheduler that monitors the time might be just a couple pages and would get triggered by each tick of the clock, but the code to load and run the scheduled app might be hundreds of pages, and be swapped out to the pagefile. It only gets pulled in when the desired time arrives.
                  Dude, seriously, WHAT handkerchief?

                  snooggums' density principal: "The more dense a population, the more dense a population."

                  Iliana: "You're a great friend but if we're ever chased by zombies I'm tripping you."

                  Comment


                  • #10
                    Re: ramdisk

                    Originally posted by ScratchMonkey View Post
                    What would cause the system to load "instance data other than the currently active application"? Presumably only the active app can load data, since other apps are waiting for data to hit RAM or on the run queue.

                    Now I can see copying RAM to disk for when the page might be needed by another app, but you don't want to use other system RAM for that, because you're just speeding up the point at which you have to page.
                    Active in terms of priority use as opposed to active on the current cycle. The goal is to keep the RAM as free as possible of data unused at the time. So windows fills the pagefile of everything of a lower priority. Though what that means is that pagefile use could be large while RAM use is small. But what that doesn't mean is that data on the pagefile will not be used in the near future, just that it's not planned on being used right now which could cause slowdowns on when it does get loaded since it'll be from the hard drive. If you want your RAM to be primarily used as opposed to the pagefile you have to set the pagefile small or non-existent. Putting the pagefile on a ramdisk makes the pagefile as fast as RAM while still allowing it to be there for programs that require a pagefile(such as photoshop). Though yeah still in most cases it would be better to get rid of the pagefile for a speed up instead of putting it on a ramdisk.

                    Quick thing on speeding up the time to a page fault, I don't think it would since to the OS those RAM pages can't be used for standard RAM access anyways. And a page fault from RAM to ramdisk would still be faster than from RAM to hard drive. That's what the ramdisk is for, stick an entire application on there and now whenever we need to page fault for data it's not back to the hard drive again. Makes the application fast while running, but slow to "start" since you have to move it to the ramdisk.

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                    • #11
                      Re: ramdisk

                      Originally posted by ScratchMonkey View Post
                      If you don't care about your data, that works fine. But if you want to be able to save your work when you run out of RAM, the pagefile lets the computer hobble along with too much stuff to fit, by simulating having more memory than you actually do.

                      There's also the case where you have a whole lot of idle apps "running" (blocked for some infrequent event). They can sit in the pagefile without affecting what you're currently working on, and will get swapped in when the event eventually happens.

                      Apps are not paged in their entirety, but in quanta of pages, typically 4k bytes. The code in a scheduler that monitors the time might be just a couple pages and would get triggered by each tick of the clock, but the code to load and run the scheduled app might be hundreds of pages, and be swapped out to the pagefile. It only gets pulled in when the desired time arrives.
                      I mean, why not just set your pagefile to 0 instead of putting your pagefile on the ramdisk. It amounts to the same thing.

                      Comment


                      • #12
                        Re: ramdisk

                        Originally posted by sordavie View Post
                        I mean, why not just set your pagefile to 0 instead of putting your pagefile on the ramdisk. It amounts to the same thing.
                        Excellent point. Or make it small enough to handle emergencies but otherwise force most data to stay in memory.

                        Here's a (short) story on Linux swap:

                        http://www.linux.com/news/software/a...nux-swap-space
                        Dude, seriously, WHAT handkerchief?

                        snooggums' density principal: "The more dense a population, the more dense a population."

                        Iliana: "You're a great friend but if we're ever chased by zombies I'm tripping you."

                        Comment


                        • #13
                          Re: ramdisk

                          If you have enough physical memory to set your page file at 0, then it does not get used much; your only possible gain would be disk space. In actual fact, you are losing out in the end because you will run out of physical memory sooner when you launch multiple memory hungry applications; when a certain threshold is reached, windows starts swapping pages out to the pagefile based on how often they are referenced, freeing memory. Without a page file, these physical memory pages are committed, therefore locked. Even if the process that holds the pages is not doing anything with them they sit there wasted.

                          The whole idea behing virtual memory is that applications should not be aware of, or be limited by the physical address space. The VMM manages physical memory by attempting to make the best possible use for it at all times.



                          DB

                          «That looks like a really nice house except for that horrible bathroom.» Donrhos

                          | |





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                          • #14
                            Re: ramdisk

                            Originally posted by Dick Blonov View Post
                            The whole idea behing virtual memory is that applications should not be aware of, or be limited by the physical address space.
                            It's true that applications should not be aware of this. But the system administrator (ie. us) should be aware of how the system is used and how to optimally allocate the resources for the kind of use we put it to. The stock swapper will sometimes have "tuning" parameters that allow us to change its strategy to match our usage. The Linux swapper has a "swappiness" parameter (see the article above) to control how aggressive it is at moving idle pages to disk.

                            If you tend to have a lot of idle apps running, a bigger swap file is a cheap way to allow that. But another approach is to simply install more physical memory to accommodate all the tasks. Which you choose depends on your budget, what the tasks do, and how responsive they need to be.
                            Dude, seriously, WHAT handkerchief?

                            snooggums' density principal: "The more dense a population, the more dense a population."

                            Iliana: "You're a great friend but if we're ever chased by zombies I'm tripping you."

                            Comment


                            • #15
                              Re: ramdisk

                              ok... after reading the discussion and other posts on the net, i have taken the pf off the ram disk, now pr loads fast again. I would put the pf back on the ramdisk if i had much more spare ram, say 16gb. I forgot to clarify in my original post that the reason for the ram disk is that i am running a 32bit system with 4gb of ram, this means that i have unused unaddressed ram. What i have now done is place windows temp files on the ram disk as well as my photoshop and illistrator scratch disks. My graphic design programs are now flying, never thought i would see such a performance increase with those programs.

                              Im still very interested in ram disks, they are very fast, just for fun i installed a small app to the ramdisk and it was almost done instantly.

                              Thanks for the posts.

                              Cheers

                              Aus
                              |TG-Irr| Aus-trooper

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