초록 ▼

A method is disclosed for maintaining consistent states of a file system. The file system progresses from one self-consistent state to another self-consistent state. The set of self-consistent blocks on disk that is rooted by a root inode is referred to as a consistency point. The root inode is stor

A method is disclosed for maintaining consistent states of a file system. The file system progresses from one self-consistent state to another self-consistent state. The set of self-consistent blocks on disk that is rooted by a root inode is referred to as a consistency point. The root inode is stored in a file system information structure. To implement consistency points, new data is written to unallocated blocks on disk. A new consistency point occurs when the file system information structure is updated by writing a new root inode into it. Thus, as long as the root inode is not updated, the state of the file system represented on disk does not change. The method also creates snapshots that are user-accessible read-only copies of the file system. A snapshot uses no disk space when it is initially created. It is designed so that many different snapshots can be created for the same file system. Unlike prior art file systems that create a done by duplicating an entire inode file and all indirect blocks, the method of the present invention duplicates only the inode that describes the inode file. A multi-bit free-block map file is used to prevent data referenced by snapshots from being overwritten on disk.

대표청구항 ▼

[ We claim:] [1.] A method for recording a plurality of data about a plurality of blocks of data stored in storage means comprising the steps of:maintaining a means for recording multiple usage bits per block of said storage means, wherein one bit of said multiple bits per block for each of said blo

[ We claim:] [1.] A method for recording a plurality of data about a plurality of blocks of data stored in storage means comprising the steps of:maintaining a means for recording multiple usage bits per block of said storage means, wherein one bit of said multiple bits per block for each of said blocks indicates a block's membership in an active file system and one or more bits indicated membership in one or more read-only copies of a file system; andstoring in said means for recording multiple usage bits per block multiple bits for each of a plurality of said blocks of said storage means.