Abstract: In accordance with at least some embodiments of the invention, a system comprises a plurality of computers coupled together and to an array of redundant storage devices that is accessible to the plurality of computers. Each of the plurality of computers comprises a local memory that stores at least one bitmap. The least one bitmap logs regions of the redundant array that have been modified.

Abstract: A method executed in a computer system for detecting and handling an invalid use of a data structure is described. The method includes the steps of providing a data structure associated with a first computing environment. The data structure includes a field having a value stored therein identifying an inaccessible address in a second computing environment. This field is used in detecting an invalid use of the data structure in the second computing environment by a computer program attempting to access memory using said inaccessible address indicated by said value contained in the first field. Additionally a preferred data structure is described as are alternative embodiments of detecting an invalid use of a data structure.