This issue occurs if there are any problems with the underlying datastore on which the snapshot is being stored. These datastores can either be NFS or VMFS. VMFS datastores are backed by LUNs accessed through FC/iSCSI/Local SCSI controllers. This error is reported if the ESXi host encounters any storage I/O errors while writing the snapshot to the datastore.
I/O to the datastores can fail for multiple reasons, such as:
- Datastore has reached its maximum capacity.
- I/Os timing out because the underlying storage is overloaded.
- Storage connectivity issues between the ESXi host and storage arrays in case of FC.
- Network connectivity issues between the ESXi host and storage in case of iSCSI and NFS.