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I'm considering a setup for a client.

GOALS

  • 10 users
  • 2 servers
  • maximum redundance (with minimal costs)
  • maximum scalability (with minimal costs)

    HARDWARE
    Here's the hardware I'm considering:

  • 2 x Dell PowerEdge R610 with Intel Xeon L5520 CPU and 8 GB RAM running VMware ESXi 4.0 Embedded from a built-in SD flash card
  • 2 x NetGear ReadyNAS 2100 with 4 x 1 TB disks in RAID 5 with 1 spare.

    I need to run two VM's for MS SBS 2008 Premium. For those who don't know it, that means DC, AD and Exchange on one server and SQL 2008 along with a custom intranet system on IIS on the other server.

    From what I've read, NFS should serve as an acceptable solution, thus enabling me to simply have the vmdk's placed on the NFS file shares.

    I would run one VM on each PowerEdge, and then one ReadyNAS for each server, with maybe 1 TB allocated to each server and then 1 TB extra for snapshots.

    BACKUP
    I plan on using the the snapshot facility on the readynas to simply backup the vmdk's, and then have those snapshots be copied to some external USB-harddrives that can manually be transported off site.

    FAILOVER
    I want the setup to be prepared for HA with ESX SMB Edition so each NAS would need to have two shares, that would each be mounted as datastores in VMware AND I'm thinking I could use rsync to replicate between the NAS'es so that each would always have a copy of the other NAS.

    SCHEMATIC
    OK let me try and illustrate.

        [VM-Host1].VM1 --runs from--> [NAS1].Share1 --rsync to--> [NAS2].Share2
    
        [VM-Host2].VM2 --runs from--> [NAS2].Share1 --rsync to--> [NAS1].Share2
    

    I'm also considering a Dell PowerVault NF500 with WSS2003R2 and an Iomega Storcenter IX4-200d or maybe the NetGear ReadyNAS PRO Business with 6 x 1 TB disks in 3 x 1 RAID 5, 2 x 1 RAID 1 and one spare. With essentially two spindle sets in each NAS I could maybe separate some stuff inside the VM's, maybe with page file on one spindle set and sql-db or exchange-db file on the other.

    Would this work as I hope? Anyone with some hands on experience, could you maybe offer some advice. Would be much appreciated.

    Allan

  • share

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    3 Answers 3

    up vote 4 down vote accepted

    It will work as you describe but I see no reason not to present the same shares concurrently to both ESXi boxes. That way you get to move your VM's around relatively easily, you wont have vMotion without the appropriate licenses and vCenter but you can still move VM's around by shutting them down, deregistering and importing them on the alternate host.

    8GB RAM is a poor choice for an R610 - you are effectively shutting off 30% of your potential memory bandwidth, it will still be a decent performer but you would be far, far better off with 12GB RAM (6x2GB RDIMM 1066 modules) because the Xeon L5520 is a Nehalem EP which has on die triple channel memory controllers that the R610 fully supports. I'd also just punt for an E5520 rather than the L5520 unless you really are looking to hit a very specific thermal envelope, the 20Watt or so difference in TDP isn't a huge win and the $200 or so you'll save will pay for the extra RAM.

    Performance wise on your NAS you are effectively delivering about 200 sustained random read IOPS \ 50 Write IOPS. That's not a lot of storage horsepower but it may be enough for your environment - a lot depends on how busy things are. My gut feeling is that your storage will start to be a significant bottleneck if you have anything over about 50 users on any single server. By contrast the R610 should be easily able to handle the CPU and memory bandwidth for a good few VM guests running this type of server, you could certainly run both VM's on the one box with ease provided the VM files are located on the two different NAS's. My recommendation to you is to pick a storage solution that gives you as many effective spindles as possible, ideally in a RAID 10 but RAID 5 with more than 5 disks in the pack at least gives you write performance that is better than a single drive, this is important for SBS as Exchange in particular is biased towards write IO more than most things.

    Your backup strategy looks OK to me but you really want to be careful about a couple of things. The main thing is that you want to do your best to quiesce the VM's disk activity and flush all outstanding disk IO before making the snapshot (so it's reasonably consistent) and secondly restoring snapshots of DC's can be a problem - specifically USN rollback can happen and that is very bad. See this earlier question regarding virtualizing DC's. Provided you never intend to have any other DC's then that isn't an issue but you need to keep it in mind.

    One final thing to think about - at this level Windows Hyper-V Server 2008 R2 gives you a pretty decent Live Migration capability for the same price as ESXi 4 - so it is worth considering.

    share
        
    Isn't ESXi 4 free? –  Chopper3 Oct 23 '09 at 22:28
    2  
    ESXi 4 is free, but HA and VMotion (the equivilent of live migration) are not. You can run the hypervisor at no cost as long as you don't want the cool goodies that come with it. –  MDMarra Oct 23 '09 at 23:06
        
    That was my point - both ESXi and Hyper-V Server are free (or have free licensing modes) but Hyper-V Server gives you Live Migration capability under the free license while ESXi needs to be paired with a licensed vCenter and licensed itself in order to enable vMotion. –  Helvick Oct 23 '09 at 23:22
        
    Yeah, I was answering Chopper. Your answer is good. –  MDMarra Oct 24 '09 at 0:59
        
    Helvick, thank you so much for your great answer, I will need some time to digest it and really understand the details of it, but let me address the suggestion with HV8R2. I chose VMware for two main reasons: 1. It doesn't require a DC to run 2. VMware supposedly performas a little better ... and I thought the embedded option was rather slick, ie. no moving disk parts in the servers themselves, meaning fewer points of failure. –  user23815 Oct 24 '09 at 11:50

    Why bother with two low spec machines, I'd be tempted to simply buy a single server with 12GB memory, an E5540 and run the VMs from local disks - it'll be MUCH faster than trying to run it from low-end NFS mounts - easier to setup too.

    share
        
    Yeah, that's a valid concern. The reason I want to go with two boxes is that I want to have an option, if one goes down, to move both VMs onto the other box and do whatever maintenance necessary. This would need to be doable without too much hassle. If the vmdk is stored on the server that goes down, I can't easily move it to the other server (since it's down, get it? :-)) but by having it stored externally, I hope to at least ease the pains a little. But then up pops the question: "what if storage goes down?" Thus, the dual NAS solution... –  user23815 Oct 24 '09 at 13:35
        
    I see what you're saying, I'm just concerned about using two cheap'ish NAS boxes rather than one, dual-controller, dual-PSU, FC box instead. Something like a HP MSA 2000fc G2 or an EVA 4400 would be SO much quicker and more reliable. Obviously they cost more than two NAS boxes but that was why I suggested saving some money on the two servers. –  Chopper3 Oct 25 '09 at 14:05

    After much consideration and talking to Dell I have decided to go with the Dell NF500, housing 4 10K SAS-disks in RAID 10 (with 1 hot-spare). They will have a 4-hour support contract, so that if a disk goes down, the hot-spare will take over and a technician will be on the spot shortly thereafter to change the disk in question. I will use the NFS protocol to access the server.

    Both app servers will be 12 GB.

    As for backup, I will attach external USB disks to the NF500 and mount that as external storage inside SBS 2008 and then I will use the built-in backup in SBS 2008. I will take snapshots of the server images before big upgrades, so that I can have easy rollback in case of failure.

    I want to thank you guys again for your advice. I think you both had some great points.

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