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VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

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  • VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

    Hi All,

    I'm suffering very slow performance in using my VM deployed on the iSCSI SAN-VMFS datastore, the following attachment shows the deployment diagram which i believe already according to the best practice around the net by segregating the network from SAN into the server.

    Code:
    http://virtualgeek.typepad.com/virtual_geek/2009/01/a-multivendor-post-to-help-our-mutual-iscsi-customers-using-vmware.html
    However, after reading the quoted article, it seems that no matter how fast the disk is, using SAN
    in a VMWare environment it will always be slow around 160 MBps

    This usually means that customers find
    that for a single iSCSI target (and however many LUNs that may be
    behind that target 1 or more), they can't drive more than 120-160MBps.

    is there anything that i should do to boost performance ?

    Thanks.
    Attached Files

  • #2
    Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

    Since, the iSCSI SAN is directly attached to the ESXi Server and each cable has it's own subnet and connected to a dedicated vSwitch see the following attachment.

    so in this case my plan is to reconfigure the following:

    1. Breakdown the LUN into smaller like (7x300GB RAID-5), instead of having one large RAID-5 LUN (14x 300 GB) and make 1 TB of VMFS shared for all of my VM.
    2. Reduce the number of network involved in the iSCSI SAN cable and connect them into the same vSwitch.

    as soon as I created the smaller LUN in no.1 above i shall create a smaller VMFS for my hi-performance VMs.

    Kind Regards,
    AWT
    Attached Files

    Comment


    • #3
      Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

      I wouldn't say that's absolutely horrible performance. 160MB/s is a lot faster than what I was getting with my swISCSI solution w/ 12 spindles and 1Gb networking.

      In some cases it's faster than an MSA1000 SAN. Take a look at all the performance numbers people submitted in this ultra long thread using IOMETER:

      http://communities.vmware.com/thread...t=400&tstart=0
      VCDX3 #34, VCDX4, VCDX5, VCAP4-DCA #14, VCAP4-DCD #35, VCAP5-DCD, VCPx4, vEXPERTx4, MCSEx3, MCSAx2, MCP, CCAx2, A+
      boche.net - VMware Virtualization Evangelist
      My advice has no warranties. Follow at your own risk.

      Comment


      • #4
        Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

        Jason,

        thanks for replying my thread,
        see the following SQLIO Random access stress test result it is really2 slow.

        I also attach the current network diagram from the ESXi console as well as the Visio deployment diagram too.

        see the result below:

        *Local HDD: 4x 500 GB SATA 7200 rpm RAID - 5 *
        C:\SQLTEST>sqlio.exe
        sqlio v1.5.SG
        1 thread reading for 30 secs from file testfile.dat
        using 2KB IOs over 128KB stripes with 64 IOs per run
        initialization done
        CUMULATIVE DATA:
        throughput metrics:
        IOs/sec: 8826.73
        _MBs/sec: 17.23 _


        while

        *SAN HDD: 14x 300 GB SAS 15000 rpm RAID - 5 *
        C:\SQLTEST>sqlio.exe
        sqlio v1.5.SG
        1 thread reading for 30 secs from file testfile.dat
        using 2KB IOs over 128KB stripes with 64 IOs per run
        initialization done
        CUMULATIVE DATA:
        throughput metrics:
        IOs/sec: 2314.03
        *MBs/sec: 4.51 *
        Attached Files

        Comment


        • #5
          Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

          Out of desperation and stress,
          I was thinking to redesign the network all over again from scratch,
          instead of having different subnet for each cable would it be better off to perform trunking ?

          directly from the ESXi Servers into the SAN to utilize 2x 1 GB Ethernet cable to boost the data performance for the VM without the use of any switch in between the SAN and Servers.

          Comment


          • #6
            Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

            Hi All,

            Based on the following article from VMWare:

            http://kb.vmware.com/selfservice/mic...rnalId=1001251
            "For any given target (iSCSI target IP), you establish one link through a NIC in the team. An additional session to a separate target (different iSCSI target IP) can establish a connection through the second NIC in the team. This is not guaranteed because it is dependent on a number of variables we cannot control. All luns presented on one IP address passes data through the connection established during the iSCSI session login."


            http://pubs.vmware.com/vi3i_i35/iscs..._reqs.4.7.html
            "Note You can configure some ESX Server systems to load balance traffic across multiple HBAs to multiple LUNs with certain active-active arrays. To do this, assign preferred paths to your LUNs so that your HBAs are being used evenly."

            Since my target is just one big target containing multiple LUN, therefore i have to accept that only one single cable that is used to access the SAN, so the other cable is just a fail over in the NIC team.

            I hope this can be a help for everyone who dig in to this forum thread.

            Kind Regards,
            Albert.
            Attached Files

            Comment


            • #7
              Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

              Here is a link that was helpful for me

              http://virtualgeek.typepad.com/virtu...ng-vmware.html

              Comment


              • #8
                Re: VMWare ESXi 3.5 u4 suffering slow performance in iSCSI RAID-5 of 15k rpm SAS SAN

                Yes, I've read that article already too.

                Comment

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