A system and method for controlling access to a shared storage device in a computing cluster having at least two nodes configured as cluster members provide fencing and quorum features without using the device controller hardware/firmware so fencing can be provided with storage devices that do not support disk reservation operations, such as with non-SCSI compliant disks. A polling thread on each node periodically reads a designated storage space on the shared storage device at a polling interval to determine if its corresponding node registration key is present, and halts the node if the key has been removed. A cluster membership agent removes a corresponding node registration key from the designated storage space of the shared storage device and publishes new membership information indicating that the corresponding node has departed the cluster only after delaying for a time period greater than the polling interval.