Snapshot technique using snapshot status table for shared storage supporting large capacity
Young-Ho Kim, Seong-In Jung, Myung‐Joon Kim · 2004
Traditional snapshot technique has some limits that adapted to a large capacity storage shared by multi-hosts in the following aspects. As volume size grows, it deteriorates crucially the performance of write operations and snapshot destruction due to the additional disk access to examine the need of COW. We introduce Snapshot Status Table of which entry is composed of First Allocation Bit (FAB) and Snapshot Status Bit (SSB) placed on memory. It improves performance of write operation and snapshot destruction reducing disk access to mapping block to know the execution of COW while snapshot is taken. Also it does not block the write operation occurred during snapshot creation.