13 Replies Latest reply: Nov 11, 2013 5:29 PM by blueblade RSS

    VDBench shows unrealistic Writes on Windows, while Perfmon/TaskManager/SANSurfer shows 0 activity

    blueblade


      Seeing very strange behavior trying to compare VDBench 5.04 numbers on Windows 2008 R2 to those monitored the system/HBA/iSCSI NIC level when doing Write IOs specifically.
      VDBench shows around 70,000 IOs per second being performed when doing writes, regardless of the transfer size or tweaking # of JVMs/threads between 8 and 24.


      With large (256K) Writes, VDBench is showing ~17,000 MB/Sec (which is not possible with 10GbE iSCSI x 2), but Task manager shows near 0% network utilization and perfmon monitoring of \PhysicalDisk(*)\Disk Transfers/sec shows basically no IOs going to the disk in question (or any other disk for that matter)

       

      I've tried two different Windows 2008 R2 systems (one using iSCSI, one using Qlogic Fibre Channel HBA), and trying both JRE 6.0 u 45 and JRE 7 u 40 runtimes.
      The Fibre Channel HBA system similarly shows 0 activity at the HBA (SANSurfer) level or via Perfmon/Task manager.

       

       

      If I change VDBench to do reads instead of writes, VDBench numbers seem to reflect reality, and I see activity at the system/HBA level that seems to agree with the numbers VDBench produces.
      An example of the param file I'm using:(showing similar iorates for all xfersizes-- the MB/Sec reported by vdbench just increases proportinatly with the xfersize)

       

       

       

       

       

       

       

      hd=localhost,jvms=8

      sd=sd1,lun=\\.PhysicalDrive11,openflags=directio,size=20g

      rd=rd1,sd=sd1,format=yes,forthreads=(8),forrdpct=(0),rhpct=0,whpct=0,forxfersize=(4k,32k,64k,256k),seekpct=100,iorate=max,elapsed=60,interval=5,pause=5

       

      Any ideas?