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Immortal
Immortal
‎03-08-2011 05:29 PM

Q: VMFS Block Sizing and NTFS

Hi Guys ~

I am hoping you guys can help me, since I am not an expert. I understand VMFS Block sizing, and how it will determine the maximum file size that can reside in that datastore.

  • 1MB block size – 256GB maximum file size
  • 2MB block size – 512GB maximum file size
  • 4MB block size – 1024GB maximum file size
  • 8MB block size – 2048GB maximum file size

I have also discovered by trial and error that if you have two datastores with different block sizes, you will get an error when trying to snapshot a VM.

Here’s my question: If the VMFS Datastore is formatted with 8MB Block sizes but the Windows OS has it’s volume formatted with the default setting, is NTFS using the 8MB Block size that is being used by VMFS?

Thanks in advance for any insight you can provide 😉

~kim

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Thiago_Moreira
Contributor
Contributor
‎03-08-2011 06:09 PM

Hi KBetter

Windows cannot see VMFS datastores directly. VMFS is the datastore where you will store VM files (hard disk files, configuration file, nvram, etc.). The VMFS block size will determine a maximum hard disk size. For example, if you use a block size of 8 MB, your guest VM will use a disk 2048GB maximum.

Windows guest will see "inside" vmdk file stored in a VMFS datastore. This vmdk file could be formatted with any file system, with any block size.

Your guests vms are entirely encapsuled in files and cannot access directly VMFS datastores. (ok, you can do this using iscsi drivers for windows.... , but this is a work around).

Take care.