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This discussion came up recently with some friends in the communities, and it had quiet an interesting outcome. The discussion was around exactly how large can you make the largest VMFS-5 single-extent volume in vSphere 5.0. Well, we are stating 64TB in our docs, but exactly how big is 64TB? We decided to find out.

As a test, three LUNs of different sizes were created. The first was 63TB, the next was 64TB and the final one was 65TB. The following is what was observed when a VMFS-5 volume was created on these LUNs:

  • 63TB

        When a volume was built on the 63TB LUN, the size of the volume that was created was 69268964114432 bytes. This equates to (( 63 * (1024 * 1024 * 1024 *1024 )) – 256MB) bytes.

  • 64TB

        When a volume was built on the 64TB LUN,, the size of the volume that was created was 70368475742208 bytes. This equates to (( 64 * (1024 * 1024 * 1024 *1024 )) – 256MB) bytes.

  • 65TB

        When a volume was built on the 65TB LUN,, the size of the volume that was created was 70368744177664 bytes. This equates to ( 64 * (1024 * 1024 * 1024 *1024 )) bytes exactly.

This is how these volumes appeared in the CLI (df command):

Df
This is how these sizes were reported in the UI:

Ui

Although both the volumes labeled 64TB & 65TB are reported with the same size in the UI, the actual sizes are different by 256MB.

However, the bottom line (and the purpose of the test) confirms that the largest single extent 64TB VMFS-5 volume size is (64 * 1024 * 1024 * 1024 * 1024) bytes.

Kudos to Tomi Hakala for doing the actual test.

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