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Improving undelete probability by changing the existing resource allocation scheme

IP.com Disclosure Number: IPCOM000028659D
Original Publication Date: 2004-May-26
Included in the Prior Art Database: 2004-May-26
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Abstract

The core idea is derived from a concept I call: "on-demand-recovery-design". Assuming that inadvertent deleting of files or directories does happen, we can help the absent minded customer by keeping around the just-freed resources (i.e file pages and inodes). To that end a new allocation scheme should be used: FirstRemovedFirstAllocated (FIFO order).

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Improving undelete probability by changing the existing resource allocation scheme

One of the most common mistakes committed by novice as well as by experienced customers is to delete the wrong files and/or directories. The various filesystems available in the UNIX* market were not designed to support an "undo" operation. If a user deletes a file or a whole directory and then creates new ones, it is very likely that the new files will be assigned the just removed file's or directory's resources (i.e. pages and inodes). The only relief for the unfortunate customer is to resort to his backup. Restoring data from backup, however, has a few drawbacks. First, the data restored is not the latest data. Second, restoring from backup (especially a centrally managed backup system like TSM ..) is a time consuming process. One way to deal with the "ought to happen" disaster in the LINUX/UNIX market is to use the versioning filesystem functionality. Keeping different versions requires proper configuration; unfortunately most incidents happen on systems that are not configured to handle such disasters. The bottom line is that versioning does indeed alleviate some of the problems, but it does not help in most cases.

    There are "undelete" utilities on the market. However, their productivity is hampered immensely if the user does not realize his mistake soon enough (i.e. stop in his tracks and not create new files!). Worse still, even in cases where the user does react promptly, t...