Swap space for kvm virtual host

Nataraj <incoming-centos@xxxxxxx> · Mon, 14 Mar 2011 14:24:07 -0700



    I have a kvm virtual host running on what will become CentOS 6 with
    12GB of memory and a Quad Xeon  X5560 2.8Ghz .  The store for
    virtual machines will be a software raid 6 array of 6 disks with an
    LVM layered on top.  I'm not initially planning any major
    overcommitment of resources, though there could be a need for some
    overcommitment with a light workload on the guests.

    
     In recent years people seem to configure a wide range of different
    swap allocations.  I was thinking initially to spread swap across
    seperate non-raid partitions on 4 of these disks, but the downside
    of that is if I put 2gb on each disk, then I can only swap processes
    that will fit in 2gb swap space.  Also, if one of the disks fails, I
    have to reboot if anything was swapped to that drive.

    
    My questions are as follows:

    
      What experience are others having with putting swap space on
        raid partitions?  I was thinking about maybe swapping on a
        raid10 device, otherwise an LVM spanning multiple drives.
      In practice, what kinds of swap allocation are people finding
        useful for a kvm virtual host of this size?

      
    I definitely don't want a system that is so overcommited that
    performance is impacted, but if some overcommitment is reasonable
    for VM's that have light workload, then I consider that.  I can
    increase system resources when that becomes necessary.

    
    Nataraj

    
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