ESX4 ZERO out disk

[isolo]

Do i need to zero out disk in VMs on ESX4, to save space while doing VCB backup? Or is it done automatically?

[Texiwill]

Hello,

Not sure really what you are asking but.... VMDK backup size is dependent on the disk being backed up. If the disk is a pre-allocated or thick disk then every block of the VMDK will be backed up including zeroed blocks. If it is a thin disk, zeroing the blocks will allocate those blocks and therefore make a full size backup of the VMDK. However, if the blocks are not allocated your backup will generally only be the blocks in use.

So I would not zero out any parts of the VMDK.

Best regards, Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009
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[isolo]

I am not sure you are correct. vcbmounter has -F switch

if -F is nto set VCB will backup only used space not the whole disk

[Texiwill]

Hello,

I think you would have to test this or you would backup 'used' but blocks that are written to all zeros which could be part of an existing file. It would 'look' like unused disk but could actually be used..... I think they mean 'unallocated' space which is how thin disks are done. Or those that are not zero-thick or zero-eager-thick disks.

Best regards, Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009
Now Available on Rough-Cuts: 'VMware vSphere(TM) and Virtual Infrastructure Security: Securing ESX and the Virtual Environment'[/url]
Also available 'VMWare ESX Server in the Enterprise'[/url]
[url=http://www.astroarch.com/wiki/index.php/Blog_Roll]SearchVMware Pro[/url]|Blue Gears[/url]|Top Virtualization Security Links[/url]|Virtualization Security Round Table Podcast[/url]