Brian Hofmeister at

Doing less with less...

September 2007 - Posts

  • MS Virtual Server - 1, VMWare - 0

    Well the title might be a little misleading but I had to capture your attention somehow. I think the actual score might be something like "MS Virtual Sever - 1, VMWare - 24".

    Anyone that knows me is well aware of my VMWare allegiance but I think they are really dropping the ball on one particular area.  Currently, VMWare is unable to resize vmfs volumes.  This is a HUGE problem for users of the ESX product. 

    Let me give a scenario that I have run in to several times already.

    I carve out some LUN space for my ESX farm and think, "No way I will ever need more than 250GB for this particular farm."  I connect my ESX servers to the lun and they format the lun using vmfs which is set at 250GB.  A few months go by and guess what, I use up 220GB of space and the remaining 30GB is practically unusable since my standard Virtual Machines are 40GB in size.

    VMWare's solution?  Well actually they have two, one of which is NOT recommended by anyone at VMWare.

    1.  Create a new lun and present it to the ESX farm.  Use the nifty EXTENT feature within the ESX farm to basically Band-Aid the new lun to the existing lun and they work as one big vmfs volume.

    Sounds good eh?  NOT RECOMMENDED by anyone at VMWare.  Just like it sounds, you are basically running your volumes in RAID0.  Half of your VM files may be sitting on 1 lun while the other half of the files sit on the other lun.  What happens if one of the luns has a hiccup and goes offline for a second.  It's basically the equivalent of unplugging one disk in a RAID0 array for one second and then plugging it back in.  Do you think the VMs will live?  Most likely not.

    2.  Create a new lun that is bigger than the original lun.  Take all your VMs offline and COPY them to this new lun.  Then delete the old smaller lun.

    Are you serious?  We have this brilliant piece of technology that is highly redundant and available but if I run out of space, I have to take the whole thing offline?


    So all you Microsofties have been reading this article and wondering, "Why does this mean MS Virtual Server is "1 up" on VMWare?"

    Microsoft Virtual Server runs its VMs on NTFS.  An NTFS volume can be resized dynamically without taking the servers offline.  I think every storage vendor has a different tool for doing this but ours is SnapDrive.

    One last thing before I finish this post... I don't like how VMWare misleads you on the web site.  Click HERE for details on VMFS.  They say:

    Dynamic increase of VMFS volume size.  Create new virtual machines without relying on a storage administrator.  Adaptive block sizing and addressing for growing files allows to increase a VMFS volume on the fly.

    That's very misleading considering the available tools/options for resizing.  This blurb should have an asterisk that says "if you like RAID0 and not being supported by VMWare".

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