2 Replies Latest reply on Jun 15, 2013 5:00 AM by JVlo

    Workstation - Make VMs Run better inside a RAMDISK

    JVlo Novice

      VMs are immensely faster when running inside a RAMDisk, however, when running a VM inside a RAMDISK I can't create snapshots.

      For example I have a 3GB XP VM and a 700MB ISO inside a 5GB RamDISK. (ImDisk is a great Ramdisk)

      Its not possible to create a snapshot. Even when powered off.

      This makes no sense because the snapshot uses little space once created, but it seems you need a lot more space while creating the snapshot.

      The error message is also crap. It doesn't say "You don't have enough free space" it gives some arbitrary error message.


      The performance is worthwhile for adding the functionality. Its at least 3-10x faster.

      VMWare should detect that it is running inside a logical disk (not on a physical disk) and it should ask "Do you want to put temporary snapshot files somewhere else?"

      Or it can simply detect that there is not enough free space and put the temp files somewhere else instead of failing miserably and mysteriously.


      Infact Workstation should do away with me needing to use a RamDisk Entirely


      Workstation should give me an option to run a VM and its ISO as much from memory as possible. I've got 16GB of RAM and will upgrade to 32GB soon.

      Memory is becoming more and more abundant. Its time to take advantage of it.


      I want to see a tickbox "Run this VM in RAM as much as possible"

      "Cache this ISO in RAM as much as possible"


      Yes windows 7 is supposed to be good at caching etc, but try a RAMdisk out. The proof of the pudding is in the eating.


      Thats my 2c. Thanks for reading.

        • 1. Re: Workstation - Make VMs Run better inside a RAMDISK
          a.p. Guru
          vExpertCommunity WarriorsUser Moderators

          A few thoughts. Although I agree that a RAM disk is probably the fastest way to run a VM, I personally decided to use an SSD for some obvious reasons, e.g. less risk, no copying required, less expensive, ...

          The reason why Workstation prevents you from creating a snapshot is safety. Since a snapshot can grow up to the size of the provisioed disk size, Workstation checks for a certain amount of free disk space. You can disable this check in the .vmx file (mainMem.freeSpaceCheck = "FALSE"), but I would not recommend it. Regarding snapshots, these are no temp files but files which grow in size depending on virtual disk activity. Placing them on another location (e.g. a HDD) wouldn't make any sense, as it would slow down the VM. All virtual disks in a snapshot chain are used! (see http://kb.vmware.com/kb/1015180)



          1 person found this helpful
          • 2. Re: Workstation - Make VMs Run better inside a RAMDISK
            JVlo Novice

            Thanks for the helpful info!

            I'll definitely try the mainMem.freeSpaceCheck = "FALSE". The VM won't change much after the snapshot.

            Geez VMWare has ridiculously bad and unhelpful error messages. I thought it simply failed, I didn't realize the reason was due to a simple free space check.



            Regarding the 2nd part of my post.

            Having the option to put as much of a VM in RAM as possible will allow massive performance improvement.

            They can just include a little warning saying "if your your PC or VMWare crashes or loses power, your data will be lost".

            Thats fine. There is plenty of VM work that is not critical. for the 1/1000 times when something crashes and you have to re-do it, you'll be happy for all the other 999 times where it ran 10x faster.

            Once you get the VM to a state you want to keep you just untick the box and it would then write the VM from RAM back to disk.

            It should be something you can do on the fly.