Comments on: Virtualization Short Take #24 http://blog.scottlowe.org/2008/12/15/virtualization-short-take-24/ The weblog of an IT pro specializing in virtualization, storage, and servers Wed, 08 Feb 2012 17:13:47 +0000 hourly 1 http://wordpress.org/?v= By: Cody Bunch http://blog.scottlowe.org/2008/12/15/virtualization-short-take-24/comment-page-1/#comment-42819 Cody Bunch Tue, 16 Dec 2008 23:27:22 +0000 http://blog.scottlowe.org/2008/12/15/virtualization-short-take-24/#comment-42819 "Ben Armstrong answers the question, “Why does it take so long to create a fixed size virtual hard disk?” The answer: the disk space is zeroed out in advance. My question is this: is this need to zero out the disk space a result of how NTFS deletes files or is this scenario applicable to VMFS as well?" Not true. At least not entirely. The default disk "Zeroed Thick", created by the vi client, ONLY zeros a block when it's written or read for the first time. "Eager Zero Filled Thick" created by vmkfstools will pro-actively zero fill it. This is something that VMFS does by default, based on the disk type created, and not specific to any guest filesystem. I should have a post describing all of this shortly. “Ben Armstrong answers the question, “Why does it take so long to create a fixed size virtual hard disk?” The answer: the disk space is zeroed out in advance. My question is this: is this need to zero out the disk space a result of how NTFS deletes files or is this scenario applicable to VMFS as well?”

Not true. At least not entirely. The default disk “Zeroed Thick”, created by the vi client, ONLY zeros a block when it’s written or read for the first time. “Eager Zero Filled Thick” created by vmkfstools will pro-actively zero fill it.

This is something that VMFS does by default, based on the disk type created, and not specific to any guest filesystem.

I should have a post describing all of this shortly.

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