9 Replies Latest reply on Jun 20, 2007 5:23 AM by OlivierTremolieres

    Persistent disk VS regular?

    Stu_McHugh Hot Shot

      When creating a new virtual hard disk for a virtual machine can someone please tell me the difference between creating a regular virtual disk without using the 'independent' check box and, checking 'independent' and 'Persistent' disk!?!

       

      I know you have to use independent and persistent to use shrink disk but I can't see the difference between the two anyway!!?

       

      Make sense?

        • 1. Re: Persistent disk VS regular?
          Champion

          Inpdependant disks are exluded from snapshots, this includes disk exports with vcbMounter, I think that's the only difference.

          • 2. Re: Persistent disk VS regular?
            GraemeRamm Novice

            From my understanding there are three disk modes.

             

            The default allows the disk to be included when a snapshot of a VM is performed. (if the disk is to be used to hold a data volume you "may not" want its data to be included in a snapshot.

             

            The other two modes are independant and can either be persistent (all data written to the disk stays on the disk, or non-persistent.  Non-persistent mode disks will revert to their original state upon a reboot of the machine (useful if you are software packaging using a snapshoting mechanism and want to keep a clean machine).

            • 3. Re: Persistent disk VS regular?
              Virtuoso

              Independent disk is a legacy feature from ESX Server 2.x.  With ESX Server 3.x, the default behavior is VM snapshots that take point-in-time states of all virtual disks and optionally VM memory.

               

              If you set a virtual disk to independent, that virtual disk is excluded from a teamed set of virtual disks comprising a snapshot.  VMs with older (legacy) virtual hardware will have virtual disks that default to independent.

               

              Independent will default to persistent mode in which case all disk data is written and committed to disk.  Setting it to undoable mode will allow you to separate the activity (written to a REDO file) and you have the option to commit or discard changes when you power off the VM.

              • 4. Re: Persistent disk VS regular?
                gakullak Novice

                And what about this question in a VCP exman? What do you think about? How can we set "Undoable Mode" from VIC ? Or only editing VMX file with "vi" ?

                 

                What are the Virtual machine's available Disk Modes: (Select all the apply)?

                 

                A. Persistent

                B. Nonpersistent

                C. Semipersistent

                D. Undoable

                E. Unchangable

                F. Append

                G. Re-do

                 

                Answer: ABDF

                • 5. Re: Persistent disk VS regular?
                  madcult Hot Shot

                  Isn't this question from a 2.x exam?!

                  • 6. Re: Persistent disk VS regular?
                    gakullak Novice

                    No.

                    It was taked from:

                     

                    Testking

                    VMware VCP-310

                    Q&A with explanations[/b]

                    The explanation is:

                     

                    ıExplanation:ı

                    ıAvailable Disk Modes:ı

                    ı- Persistent - Disks in persistent mode behave like conventional disk drives on your

                    physical computer. All data written to a disk in persistent mode areı

                    ıwritten out permanently to the disk.ı

                    ı- Nonpersistent - Changes to disks in nonpersistent mode are not saved to the disks, but

                    are lost when the virtual machine is powered off or reset. Nonpersistent mode is for users

                    who want to start with a virtual machine in the same state. Example uses include providing

                    known environments for software test and technical support users, as well as

                    demonstrating software.ı

                    ı- Undoable - Changes to disks in undoable mode can be saved, discarded, or appended

                    when the virtual machine powers off.ı

                    ı- Append - Changes to disks in append mode are preserved in a redo log attached to the

                    virtual disk.

                    • 7. Re: Persistent disk VS regular?
                      OlivierTremolieres Hot Shot

                      I'm interested by your response. You say "Setting it to undoable mode will allow you to separate the activity (written to a REDO file) and you have the option to commit or discard changes when you power off the VM.", but I can't see this option in Virtual Center. How can you active this mode ? I'm very interested because REDO is very quick, quicker than Snapshot, and doesn't need lot of disk space to work.

                       

                      Regards,

                       

                      Olivier

                      • 8. Re: Persistent disk VS regular?
                        Texiwill Guru
                        User ModeratorsvExpert

                        Hello,

                         

                        ESX v3 and VC v2 has only 2 MOdes:

                         

                        Normal (snapshotable) or Independent. Within in independent you have only 2 different modes: persistent vs non-persistent.

                         

                        Append or undoable are no longer available with ESX v3 and VC2

                         

                        Best regards,

                        Edward

                        • 9. Re: Persistent disk VS regular?
                          OlivierTremolieres Hot Shot

                          Thank you very much.

                           

                          Olivier