3 Replies Latest reply on Jul 19, 2008 4:55 AM by Paul Thomas

    Partitions or vdisks

    rhsoftware Hot Shot

      Has anyone an idea what will bring a better performance (1 physical disk on the host)

       

      • Split a virtual disk in some partitions (/var/log, /tmp, /var/cache, swap)

      • Add for each mount-point a seperate vmdk

       

      I think more vdisks can have a performance gain if there is I/O on more than one because there is more than one file-handle inside vmware, but i'm not sure that there is no overhead having more virtual hardware and what is better. OK if you can place the vmdk-files on more than one physical disk you will win - but i need a basic setup which will run simply on one disk at begin.

       

      We will use ESX in some weeks and so i should make a golden-master-setup with best settings and its not easy to test such things before getting real load on the machine - simulating lod often will not be the same as production-load

       

        • 1. Re: Partitions or vdisks
          Peter_vm Guru

          It doesn't matter since you have still only one spindle.

          But if you get more of them, surely separate file systems accordingly and have virtual disks spread across multiple physical drives.

          • 2. Re: Partitions or vdisks
            Paul Thomas Master

             

            I think the main limitation is the speed of the disk.  I've found virtualisation needs lots of fast disks.

             

             

            You may even make things slower if you partition the disk as you could end up placing files further away from each other on the physical surface of the disk.  I'm not sure how much difference it would make, but wwe used to worry about such things alot in mainframe days! e.g putting the busiest partition in the center of the disk to minimise head movement.

             

             

            • 3. Re: Partitions or vdisks
              rhsoftware Hot Shot

              OK, i think it will be the best to make own vmdks for /tmp, swap, /var/log, /var/cache and /data

              If there is no overhead for the vmware-server as you said to have more disk devices me feeling says me it maybe less overhead to write in sepearte disk-files instead scheduling wrtie-access on one big.

               

              I want sepearate disks/partitions especially for /var/log to prevent filling the system-disk nearly 100% if something goes wrong in the guest and kill the system, on physical machines that will follow in fragmentation - I dont know if fragmentation matters in a virtual disk, but sure it makes nothing better