11 Replies Latest reply on Jun 6, 2007 9:48 AM by IdeCable

    Slow virtual disk problem

    BigHug Hot Shot

      Hi, there:

      We run VMware server 1.0.1 on a Win2k3 SP1 host. The VM is also Win2k3 SP1. We are experiencing very slow I/O problems. When copying a big file in the same directory, it will take 4 to 6 times longer in the virtual disks than in the host. For example, copy a 500-MB file will take 50 seconds on the host drive. However, it will take 280 seconds on the virtual dirve, which is located on the same host drive.

       

      The VM uses LSI driver for the SCSI controller. The virtual disks are all preallocated. The host is a HP HCL server.

       

      Any help will appreciate. Thanks.

        • 1. Re: Slow virtual disk problem
          KevinG Guru

          Any error(s) reported in the vmware.log file regarding access issues with the virtual disk?

          • 2. Re: Slow virtual disk problem
            Peter_vm Guru

            What host CPU utilization do you get when you perform a large file copy in your VM?

            • 3. Re: Slow virtual disk problem
              BigHug Hot Shot

              OK, more information...

               

              The CPU utilization is about 4% to 6% on the host and 2% or 3% on the VM.

               

              In the vmware.log, there are a lot of the following messages:

               

                vmx| SCSI0:0: Command READ(10) took 1.040 seconds (ok)

                vmx| SCSI0:0: Command READ(10) took 1.110 seconds (ok)

               

              There are also WRITE messages.

               

              On the other Win2k VM on the same host, the I/O is pretty good. And I don't see the SCSI READ and WRITE messages in the log. I think these messages might indicate the problem.

              • 4. Re: Slow virtual disk problem
                BigHug Hot Shot

                OK, something is weird. I gave the VM 1 more CPU and hoped the problem will go away. But it didn't. So that I changed it back to single process VM. And the slowness problem went away. I don't see the SCSI read/write messages in the log any more. I'll run more tests tomorrow and post back the result.

                 

                This slowness problem has bothered us for several weeks. This VM reboots every night and the problem always exists.

                 

                BTW, now the VM shows "ACPI Multiprocess PC" in the device manager. How can I change it back to "ACPI Uniprocess PC"?

                 

                Thanks.

                • 5. Re: Slow virtual disk problem
                  larstr Virtuoso
                  vExpert

                  BTW, now the VM shows "ACPI Multiprocess PC" in the

                  device manager. How can I change it back to "ACPI

                  Uniprocess PC"?

                   

                  Check this thread:

                  url=http://www.vmware.com/community/thread.jspa?threadID=29415&tstart=0How to repeatedly upgrade Windows 2003 to SMP and revert to uniprocessor[/url]

                   

                  Lars

                  1 person found this helpful
                  • 6. Re: Slow virtual disk problem
                    BigHug Hot Shot

                    Bad news! The slowness problem doesn't go away. I tested it last night. It was OK. But It became slow again this morning. The VM gets reboot every night.  It's possible the OS reboot messed things up. I'll try a power off/on later when the users are away.

                     

                    Besides the SCSI messages I didn't find any error in the vmware.log. Are these SCSI messages normal?

                     

                    BTW, The other win2k VM using Buslogic driver doesn't have the slowness I/O problem.

                     

                    Lars, thanks for the link. I'll check it up.

                     

                    Thanks for any help.

                    • 7. Re: Slow virtual disk problem
                      BigHug Hot Shot

                      OK, the other win2K VM also has the I/O slowness problem. After rebooted the guest OS, the I/O was OK. But after let it run for a while, the I/O slowness will occur until reboot it again. Whenever this slowness happens, the vmware.log will show those SCSI Command READ/WRITE messages. Does any one know if these messages are normal or not?

                       

                      I'll reboot the host tonight and see what happens.

                       

                      Thanks for any help.

                      • 8. Re: Slow virtual disk problem
                        devzero Master

                        how much memory does your VM have ?

                         

                        you may open your .vmx file and set mainmem.usenamedfile="FALSE" - power down and re-start your VM and see if this makes a difference! please report!

                         

                        hth

                        roland

                        • 9. Re: Slow virtual disk problem
                          BigHug Hot Shot

                          Hi, Roland:

                          The host has 4 GB. One VM has 2 GB and the other VM has 1 GB.

                           

                          OK, I disable memory page trimming, usenamedfile and page sharing. Let's see what   happens tomorrow. I'll report back.

                           

                          Thanks for your help.

                          • 10. Re: Slow virtual disk problem
                            BigHug Hot Shot

                            OK, the slowness problem is resolved. The Vm's are really flying now. I think set usenamedfile to false help a lot. Thanks Roland.

                             

                            However, since I also disabled memory page trimmimg and TPS. The host memory usage is really high now. I'm thinking about enabling memory page trimming and/or TPS to release some memory to the host or other VM's. Does any on have comments on these 2 parameters? I did some researches. It looks like disable them will help performance. But how much do them help (a liitle or a lot) is not very clear?

                             

                            Thanks for any comment.

                            • 11. Re: Slow virtual disk problem
                              IdeCable Novice

                              By the way I run a domain controller inside a VMware Server 1.0.3 and one of the good thing that fixed disk performance was not only to disable the memory trimming option but to disable the write cache over each virtual hard drives.