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  • vmware server HD performance question

    I am about to build a new VM server, which will likely be a dual quad core xeon intel system with 32g ram, running server 2003 x 64 as the base OS. I will be running at least 8 VMs, 4 of which i really care performance and reliability wise.

    I am wondering, am I better off making one 4 or 5 drive Raid array(likely raid 5), or each VM on its own drive. In either case the main OS will be on a seperate drive. I like the raid route, because of the automatic reduncancy. My question is how much will performance suffer using a 5 drive raid 5, vs each VM on its own drive(talking about the 4 production ones). I will likely be using SATA raptors, or 15k SAS drives either way. The 4 VMs include: a citrix server, a domain controller/email server/SQL server, a web server, and a citrix web gateway server.

  • #2
    Re: vmware server HD performance question

    real raid controller, SAS disks and raid10 or 50
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    Last edited by DYasny; 6th March 2011, 19:16.
    Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

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    • #3
      Re: vmware server HD performance question

      I wouldn't bother too much with isolating the VMs. Particularly because some of the VMs won't benefit much disk I/O-wise from isolation and you'd be wasting precious resources on them. The VMs that I'd be concerned about for disk I/O are SQL and Exchange (it will depend on number of users and patterns of use obviously). I'd go with a RAID5 array or better, the more active spindles in the array the better the disk I/O.
      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.

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      • #4
        Re: vmware server HD performance question

        Thanks! One other question. Would 10k SATA be sufficiant or would i see a huge improvement going wtih SAS?

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        • #5
          Re: vmware server HD performance question

          that mostly depends on the controller you will use
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          Last edited by DYasny; 6th March 2011, 19:16.
          Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

          BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

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          • #6
            Re: vmware server HD performance question

            Originally posted by rpcblast View Post
            Thanks! One other question. Would 10k SATA be sufficiant or would i see a huge improvement going wtih SAS?
            Go with SAS if you want the better performance.

            SATA is cheaper storage and its performance is reflected as such partially due to its lower RPMs. I also subscribe to the notion that SATA/IDE is more failure prone than comparable SCSI alternatives which are better suited for higher workloads for longer durations.

            Jas
            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.

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            • #7
              Re: vmware server HD performance question

              this is a common mistake

              actually, research shows sata and sas are basically at the same level when it comes to failure. however, since sas uses the scsi protocol, the data safety in transactions is higher.

              sata is faster when it comes to random seeks, while sas is faster on the sequetial size, so sas is better for servers, especially database servers.

              the advantage of sas is there since the good controllers are all designed for sas, and can work with sata through interposers, converting scsi to ata, where performance realloy suffers due to the conversion overhead.

              the size advantage of sata is also gone nowadays, since near-line sas has been introduced - you get the same sizes as with sata, but with all the good sides of SAS

              btw, if you compare sata to scsi disks, you will definitely see better performance on sata, since scsi is sharing the data bus between drives, while sata is serial - separate bus for every drive. that had been redeemed by the SAS technology of course.

              anyhow, any serious controller you will buy, will be based on the scsi protocol, so SAS is the way to go. if you are using cheap crappy sata controllers, you better stick with sata of course.

              here?s a good objective comparison: ftp://ftp.compaq.com/pub/products/se...ata-vs-sas.pdf

              and some more reading material: http://www.google.ie/search?q=sata+vs+sas
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              Last edited by DYasny; 6th March 2011, 19:17.
              Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

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              • #8
                Re: vmware server HD performance question

                Good points, but I would like to add higher spindle counts play in the equation. Since SATA drives come in much higher densities than SCSI, a person needing 3TB of disk may quickly purchase 3x1TB SATA drives instead of 21x146GB SCSI drives. Note the incredible spindle count difference and with that, the SCSI configuration will run circles around around the SATA drives and in the event of a drive failure/replacement exercise, the 146GB drive will regenerate much faster than the 1TB drive.

                Jas
                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.

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                • #9
                  Re: vmware server HD performance question

                  well, just imagine the difference in price

                  and as I said, near-line SAS comes in the same sizes as SATA
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                  Last edited by DYasny; 6th March 2011, 19:18.
                  Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

                  BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

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                  • #10
                    Re: vmware server HD performance question

                    Thanks all for your input. One last thing. I might be going with ESXI now that its free, and was looking to do this: Install the ESXI OS itself on a pair of 10k raptors in raid 1, then have a 4 10k raptor raid 5 array for the VMs. Is this a good way to go about it and are there any issues doing it this way, vs having everything just on one raid 5 array?

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                    • #11
                      Re: vmware server HD performance question

                      Originally posted by rpcblast View Post
                      Thanks all for your input. One last thing. I might be going with ESXI now that its free, and was looking to do this: Install the ESXI OS itself on a pair of 10k raptors in raid 1, then have a 4 10k raptor raid 5 array for the VMs. Is this a good way to go about it and are there any issues doing it this way, vs having everything just on one raid 5 array?

                      I will be running at least 8 VMs, 4 of which i really care performance and reliability wise.
                      Your RAID1 array is fine. No problems there as long as the hardware is compatible with ESXi.

                      As far as your 4 disk RAID5 array, it sounds like a good start rpcblast but without hard numbers and specific baseline performance metrics and statistical use patterns from your VM candidates, our performance discussions are somewhat ambiguous and I make no guarantees that the 4 10KRPM drives in a RAID5 array will completely satisfy your performance needs. Just keep in mind that adding additional spindles and more RPMs in the RAID5 array will increase your disk I/O throughput and lessen the liklihood of disk bottlenecks.

                      Jas
                      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.

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                      • #12
                        Re: vmware server HD performance question

                        I have done some reading that suggests that raid 10 performs a lot better then 5. Is this true when going above 4 drives? I am still a lil ways away from building this server and I just wanna make sure I get it right.

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                        • #13
                          Re: vmware server HD performance question

                          RAID10 generally performs better than RAID5, but as Jason pointed out, without specific performance data you can't make a blanket statement for one over the other.

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                          • #14
                            Re: vmware server HD performance question

                            raid10 performs faster than raid5, but not over 4 drives
                            the optimal numbers of drives are 8-10

                            just think - parity and mirroring slows io down
                            increase in amount of spindles speeds io up

                            raid5 means some parity, byt four spindles
                            raid10 means mirroring + spindles. but with 4 disks, what you get is slowdown because of the mirroring over two disks, as well as speedup because the raid0 is spread over two disks. no serious increase at all. now as you add mode disks to raid10, the speeds will grow, and the mirroring overhead will become negligible. up to a point where you have too many drives, and the overhead starts to become a nuisance. Kind of a Gauss bell
                            so for every raid level there is an optimal amount of disks
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                            Last edited by DYasny; 6th March 2011, 19:19.
                            Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

                            BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

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                            • #15
                              Re: vmware server HD performance question

                              RAID10 is going to significantly increase your disk costs.
                              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.

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