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vCenter Server 4.0 VMotion operation fails with the error: Insufficient disk space on datastore
Symptoms
- A VMotion operation fails
- When attempting to migrate, you see the error:
“Insufficient disk space on datastore ”.”
Resolution
Cause
This issue may occur during a vMotion operation because vCenter Server 4.0 requires enough space to store two full-size copies of the virtual machine swap file simultaneously. If there is not enough space in the datastore, you receive this error.
For example, a virtual machine file with 8 GB of memory and a 2 GB reservation requires a swap that is 6 GB in size. You therefore temporarily require another 6GB, or a total of 12 GB.
Resolution
To resolve this issue, you must ensure that you have adequate amount of space on the datastores. To free up space, consider:
- Increasing capacity
- Moving virtual machines to other storage
- Adding additional datastores
- Removing old snapshots
- Cleaning up VMware VMFS
For more information about these operations, see Issues when a datastore or VMFS volume is full or near capacity (1003412).
Workaround
Since only the non-reserved memory uses the swap file, you can temporarily increase the memory reservation of the virtual machine to match the allocated memory while conducting the vMotion.