255GB Memory Limit for VMs with vSphere

Posted: July 15, 2010 in VMware
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“Why has a vSphere VM max mem 255GB? VMFS block size of 1MB = 256GB max – 0.4MB VM state = 255.6MB rounded down to 255GB – from Ole@VMware”

In other words, the maximum memory size for a vSphere VM is 255 GB. This is the maximum memory size because a swap file needs to be created as well. This swap file cannot exceed the maximum file size of a 1MB blocksized VMFS volume. Max file size = 256GB – VM state(roughly 400MB)=255.6GB. For safety this has been rounded down to 255GB. Which at first sounds like a weird amount but actually makes sense when you read the explanation.

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