AAshred: High Performance Secure Deletion Method for VM Environment

Secure deletion is crucial for discarding sensitive files. Users usually run rm command to delete such files. The command has security problems because data stays on disk even after execution. Secure deletion process overwrites random data to discard sensitive files. The process is executed by two methods, one is entire write method, the other is partial write method. The entire write method overwrites entire file even in the case of sparse file having data partially. The partial write method overwrites only the extent areas having data. However, the write I/O access sometimes becomes random; thus, the execution time may become longer. In this paper, we propose Allocation Aware shred (AAshred) method which achieves high performance secure deletion method for sparse files. AAshred method combines these two methods. We implemented the partial write method to shred command and evaluate the performance of the entire write method and the partial write method under various conditions. We concluded that AAshred method should use the entire write method under certain conditions that the extent ratio is over 80%, and the hole size is from 12KB to 128KB.