VMWare 10k vs 15k disks

Posted on 2012-09-10
Last Modified: 2012-09-10

I have a vmware cluster, one with 10k disks for OS and the other with 15k disks for OS (both mirrored). I see a huge difference in upload speed with the 15k like double.

All of our data is stored on disk shelfs. So my question is what is the benefit of having fast OS drives for the VMWare kernal operations also when they are clustered in vCenter and one server has 10k and the other 15k.

I'm asking because I may be able to ship faster drives so all servers in the cluster match, but if the VMWare kernel doesn't really do anything since the disk shelfs are handling all IOPs, then I can live without it.

Question by:snyderkv
    LVL 33

    Expert Comment

    the VMkernel will come into play in 2 things when doing large and massive Network transfers and Kernel swapping occurs,
    In your case I can see kernel swapping, but this happens when no memory is available to serve the VMs and you are doing over subscription, if you are not doing that, then I don't see the point for upgrading the VMkernel drives..again 15K will be faster and better :).
    LVL 116

    Assisted Solution

    by:Andrew Hancock (VMware vExpert / EE MVE)
    I would recommend 15k drives, if you have the budget.

    Author Comment

    Busbar, so vMotion tasks, fault tolerance traffic exc are handled by the disk shelfs IOPs and the two 10GB FCoE cables from each host? No kernal comes into play here?

    When you say Network transfers that affect the Kernel, what types of tasks would I be doing?

    And we have plenty of memory, are R610 resources are usually 10% used
    LVL 33

    Accepted Solution

    again all of that is considered network transfer and there is a delay because all of these IOs goes from the VMM to the kernel to the device, the delay is not noticeable but there is a delay caused by the kernel, part of that delay is the IOs the the kernel does and that is affected by disk speed.

    but how much is the delay, and how much you do FT and VMotion and do you have any issues with these right now, this is the question.
    The easy answer as I said and Hanc did that buy the 15K drives, but in my background; everything needs to be justified.

    Author Comment

    Gotcha, thanks guys

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