A hosting partition update mechanism allows updating the I/O capability of a logically-partitioned computer system in a way that minimally affects the performance and availability of I/O in the computer system. When an update is needed, a new hosting partition is created with the desired update(s). The I/O adapters in the current hosting partition are then migrated to the new hosting partition. The migration of an I/O adapter from the current hosting partition to the new hosting partition is relatively fast, thereby minimally impacting system performance and availability of I/O. Once all of the I/O adapters have been migrated to the new hosting partition, the current hosting partition may be kept as a backup, or may be eliminated. Providing a new or backup hosting partition allows updates to be performed in the new or backup hosting partition in a non-disruptive manner while the current hosting partition continues to service I/O requests.