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Thread: Vmware KB article - spot the huge error

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    Vmware KB article - spot the huge error

    http://kb.vmware.com/selfservice/mic...rnalId=1005418

    I'll give you a clue - it's under considerations.
    This is a pretty big error as I was also told the same rubbish in my VMware training.
    Passing on old wives tales like that without at least checking sources is unforgivable. That's almost as bad as Microsoft's own Exchange 2003 training book having an entire excersise about changing the eschange services to use an exchange service account that was impossible to complete and wasn't possible since Exchange 5.5
    "In a perfect world... spammers would get caught, go to jail, and share a cell with many men who have enlarged their penises, taken Viagra and are looking for a new relationship."

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    Re: Vmware KB article - spot the huge error

    a full format shouldn't inflate the volume - but a defrag will.
    my Virtualisation Blog http://jfvi.co.uk Virtualisation Podcast http://vsoup.net

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    Re: Vmware KB article - spot the huge error

    As I understand it, the most egregious error is
    the Microsoft Windows format tool writes information to all of the sectors on the disk
    I could be wrong, but my understanding is that a full format reads every sector of the disk, but doesn't normally write anything. The question then would be how a thin-provisioned disk handles requests for a read from disk space it hasn't allocated yet...

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    Re: Vmware KB article - spot the huge error

    Quote Originally Posted by scaryjim View Post
    I could be wrong, but my understanding is that a full format reads every sector of the disk, but doesn't normally write anything. The question then would be how a thin-provisioned disk handles requests for a read from disk space it hasn't allocated yet...
    Thin provisioning "lies" to the controller and only allocates the data on the underlying disk when it gets a write, reads are just faked.

    With regards to the format, I dont know, but Ive never seen VMWare expand a disk to its full size just because of a format, it usually only grows a small amount, enough for the filesystem structures and any default data.

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    Re: Vmware KB article - spot the huge error

    Quote Originally Posted by scaryjim View Post
    As I understand it, the most egregious error is

    I could be wrong, but my understanding is that a full format reads every sector of the disk, but doesn't normally write anything. The question then would be how a thin-provisioned disk handles requests for a read from disk space it hasn't allocated yet...
    Quote Originally Posted by BobF64 View Post
    Thin provisioning "lies" to the controller and only allocates the data on the underlying disk when it gets a write, reads are just faked.

    With regards to the format, I dont know, but Ive never seen VMWare expand a disk to its full size just because of a format, it usually only grows a small amount, enough for the filesystem structures and any default data.
    Bingo!

    This wrong impression that a full format zeroes the disk was what I was told at my VMware training last year as well.
    Anyone that doubts that a full format writes the same amount as a quick format just needs to do a full format on a thin provisioned virtual machine.
    As another interesting point, HP RAID arrays on their smartarray controllers also lie to windows. The full format progress bar is a blur, just like on a vmware thin provisioned disk.
    I would guess that a thick provisioned disk also lies but have no idea what an eagerzeroedthick disk will do as it makes sense that it would actually tell the truth.
    "In a perfect world... spammers would get caught, go to jail, and share a cell with many men who have enlarged their penises, taken Viagra and are looking for a new relationship."

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    Re: Vmware KB article - spot the huge error

    Quote Originally Posted by Moby-Dick View Post
    a full format shouldn't inflate the volume - but a defrag will.
    Defragging in a virtual environemnt - about as advisable as running a scheduled A/V scan on all servers at once!
    "In a perfect world... spammers would get caught, go to jail, and share a cell with many men who have enlarged their penises, taken Viagra and are looking for a new relationship."

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    Re: Vmware KB article - spot the huge error

    You may scoff , but its possible - think about desktops.

    That said there are ways of defragmenting a thin provisioned VM but you have to be clever about it
    my Virtualisation Blog http://jfvi.co.uk Virtualisation Podcast http://vsoup.net

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    Re: Vmware KB article - spot the huge error

    Quote Originally Posted by Moby-Dick View Post
    You may scoff , but its possible - think about desktops.

    That said there are ways of defragmenting a thin provisioned VM but you have to be clever about it
    Indeed, I have done it in the past. It does involve a lot of shuffling data about and a lot of zeroing though.
    "In a perfect world... spammers would get caught, go to jail, and share a cell with many men who have enlarged their penises, taken Viagra and are looking for a new relationship."

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