As most of you know, when VMware Consolidated Backup dumps image level backups VCB only dumps used diskspace. Unfortunately for us VCB does this by checking at block level if it contains only zero’s or not. If it contains only zero’s the block is considered empty, but an Operating System doesn’t zero out the disk space that contained the files when a file is deleted. An Operating System only clears the pointers to these files. This is why you could have a disk with only 4GB of used space and a 6GB VCB dump. As of ESX 3.0.2 update 1 VMware reintroduced the shrink option in VMware Tools. Kind of a weird name “shrink” cause the vmdk doesn’t actually shrink, the unused space is just zeroed out.
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