Orlov block allocator

Abstract: The present invention provides a system and method for restoring a single file from a snapshot without the need to copy every individual block or inode from the snapshot. A file restore process duplicates the inode of a file within the active file system and performs a reconciliation process between the blocks of the twin inode and the snapshot inode. If the file does not exist within the active file system, a new buffer tree is created that points to the data blocks stored in the snapshot.

Abstract: A system and method for detecting errors during the storage and retrieval of file information between a file cache system and a host computer system utilizes a block check sequence key as redundant data included in each block of file data transferred. The block check sequence key is generated by key generation logic and accompanies each block of file data stored in the file cache system by the host computer system. The block check sequence key is a compressed representation of the data within the selected block, as well as unique file and block identification information supplied by the requester of the write operation. When the block is retrieved from the file cache system, the system generates a new block check sequence key based on the data within the retrieved block and the unique file and block identification information supplied by the requester of the read operation. Validation logic ensures that if the retrieved key and the newly generated key does not match, an error signal is activated.

Abstract: An object-based storage may employ a transactional interface and a copy on write protocol. The inode for the file (which is identified by the I-number and indicates one or more blocks storing the file data) may be copied to a working copy of the inode, and the working copy may be updated to indicate the newly allocated blocks. In response to a file commit (e.g. a file close or a file synchronization command), the working copy of the inode may be atomically written to a non-volatile storage. In this manner, the updates performed during the transaction may be atomically committed to the file. The inode itself may be stored in a file (referred to as the inode file), and the storage may perform updates to the inode file atomically as well. The inode file may be modified using the copy on write protocol described above, and the master inode (mapping the blocks of the inode file) may be atomically written to non-volatile storage to atomically update the inode file. In one particular embodiment, the storage employs a journal technique for updates to the inode file.

Abstract: Memory allocator combines private (per thread) sets of fixed-size free blocks lists, a global, common for all threads, set of fixed-sized free block lists, and a general-purpose external coalescing allocator. Blocks of size bigger than the maximal fixed size are managed directly by the external allocator. The lengths of fixed-size lists are changed dynamically in accordance with the allocation and disallocation workload. A service thread performs updates of all the lists and collects memory associated with terminated user threads. A mutex-free serialization method, utilizing thread suspension, is used in the process.