Abstract: A method of managing CPU cores in a data storage apparatus (DSA) configured to perform both host I/O (Input/Output) processing and background storage processing is provided. The method includes (a) selectively classifying background storage tasks in one of a first classification for longer-running tasks and a second classification for shorter-running tasks; (b) selecting CPU cores that are running fewer than a threshold number of first-classification background tasks to process host I/O requests; and (c) processing the host I/O requests on their selected CPU cores. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: Embodiments are directed to techniques for performing deduplication. A method includes (a) obtaining a digest of a data block logically-positioned within a filesystem, the digest providing a hash value of data of the data block, (b) searching a Most Wanted Digest Cache (MWDC) within system memory for the digest, (c) locating an entry in the MWDC using the digest, wherein this locating indicates that the data block has the same data as another data block located elsewhere within the filesystem, the other data block having been previously persistently-stored, the entry having been added to the MWDC in response to the other data block having been deduplicated at least a plurality number of times, (d) locating a mapping structure referenced by the entry located from the MWDC, the mapping structure providing metadata about the other data block, and (e) deduplicating the data block and the other data block with reference to the located mapping structure.

Abstract: A technique for managing metadata in a data storage system includes receiving a set of data to be stored in a file system of the data storage system and calculating values of metadata blocks that the file system will use to organize the set of data in the file system. The technique aggregates values of the metadata blocks and sends them in a single, atomic transaction to a persistent cache. The transaction either succeeds, in which case the persistent cache stores the values of all of the metadata blocks, or it fails, in which case the persistent cache stores none of the values of the metadata blocks. Over time, the persistent cache flushes the values of the metadata blocks to a set of non-volatile storage devices that back the metadata blocks in the data storage system.

Abstract: A technique for storing data in a data storage system detects that a read is being performed pursuant to a data copy request. In response, the data storage system stores a digest of the data being read in an entry of a digest cache. Later, when a write pursuant to the same copy request arrives, the storage system obtains the entry from the digest cache and completes the write request without creating a duplicate copy of the data.

Abstract: Embodiments are directed to techniques for performing deduplication. A method includes (a) obtaining a digest of a data block logically-positioned within a filesystem, the digest providing a hash value of data of the data block, (b) searching a Most Wanted Digest Cache (MWDC) within system memory for the digest, (c) locating an entry in the MWDC using the digest, wherein this locating indicates that the data block has the same data as another data block located elsewhere within the filesystem, the other data block having been previously persistently-stored, the entry having been added to the MWDC in response to the other data block having been deduplicated at least a plurality number of times, (d) locating a mapping structure referenced by the entry located from the MWDC, the mapping structure providing metadata about the other data block, and (e) deduplicating the data block and the other data block with reference to the located mapping structure.

Abstract: A technique for storing data in a data storage system detects that a read is being performed pursuant to a data copy request. In response, the data storage system stores a digest of the data being read in an entry of a digest cache. Later, when a write pursuant to the same copy request arrives, the storage system obtains the entry from the digest cache and completes the write request without creating a duplicate copy of the data.

Abstract: A system and method verifies and restores the consistency of inode to pathname mappings. In a first embodiment, an off-line verification procedure is modified to verify and correct the primary name inode to pathname mapping information within inodes of a file system. In a second embodiment, an on-line file system verification process is modified to verify inode to pathname mapping information upon the loading of each inode within the file system.

Abstract: A system and method maintains mappings from data containers to their parent directories within a file system of a storage system. Each inode is modified to include a primary name data structure comprising a parent directory inode and a parent directory cookie value. The parent directory cookie value identifies a particular directory entry within a specified block of a directory identified by parent directory inode. An alternate name file is utilized to store alternate names, such as those associated with hard links.