Abstract: Systems and methods for a content addressable cache that is optimized for SSD use are disclosed. In some embodiments, the cache utilizes an identifier array where identification information is stored for each entry in the cache. However, the size of the bit field used for the identification information is not sufficient to uniquely identify the data stored at the associated entry in the cache. A smaller bit field increases the likelihood of a “false positive”, where the identification information indicates a cache hit when the actual data does not match the digest. A larger bit field decreases the probability of a “false positive”, at the expense of increased metadata memory space. Thus, the architecture allows for a compromise between metadata memory size and processing cycles.

Abstract: In general, in one aspect, a method for managing data in a data storage system includes receiving identifiers corresponding to different respective entries of a map stored in the data storage system, with a particular identifier corresponding to a particular entry of the map, the particular entry including a computed value corresponding to a particular portion of data stored in the data storage system and metadata indicating a location where the particular portion of data is stored in the data storage system, selecting, according to a first selection criterion, at least some of the identifiers for storage in a first portion of an index, and selecting, according to a second selection criterion, at least some of the identifiers for storage in a second portion of the index.

Abstract: Systems and methods for a content addressable cache that is optimized for SSD use are disclosed. In some embodiments, the cache utilizes an identifier array where identification information is stored for each entry in the cache. However, the size of the bit field used for the identification information is not sufficient to uniquely identify the data stored at the associated entry in the cache. A smaller bit field increases the likelihood of a “false positive”, where the identification information indicates a cache hit when the actual data does not match the digest. A larger bit field decreases the probability of a “false positive”, at the expense of increased metadata memory space. Thus, the architecture allows for a compromise between metadata memory size and processing cycles.

Abstract: In general, in one aspect, a method for managing data in a data storage system includes receiving identifiers corresponding to different respective entries of a map stored in the data storage system, with a particular identifier corresponding to a particular entry of the map, the particular entry including a computed value corresponding to a particular portion of data stored in the data storage system and metadata indicating a location where the particular portion of data is stored in the data storage system, selecting, according to a first selection criterion, at least some of the identifiers for storage in a first portion of an index, and selecting, according to a second selection criterion, at least some of the identifiers for storage in a second portion of the index.

Abstract: The present invention provides a system and method for creating and accessing a copy of one or more host-accessible storage entities contained in a persistent consistency point image (PCPI) of a volume served by a storage system. The storage entity may comprise a file system, logical volume, volume group, or “file system on raw device”. The copy of the storage entity is generated using a logical unit number (lun) copying technique in conjunction with a PCPI table of contents (PTOC). The PTOC contains data describing contents of the PCPI, including luns of the storage entity. The PTOC is written to the volume of the storage system, which is configured to store the luns, i.e., in the context of an active file system, immediately prior to generation of the PCPI. After generation of the PCPI, the PTOC is deleted from the volume such that it is only stored within the PCPI and not within the active file system.

Abstract: Redundant solid-state memory devices are used to enhance the operation of a network storage system. To reduce the likelihood of substantially concurrent failure of two or more such memory devices, write allocation decisions are made so as to influence the wear on the various solid-state memory devices, so that not all of the solid-state memory devices wear out at the same rate. This can be accomplished by skewing the wear caused by erases/writes, across the solid-state memory devices, so that the devices experience unequal wear and, therefore, do not all fail at or approximately at the same time. The roles of the various flash devices are adjusted when a solid-state memory device is replaced, such that subsequent write allocation decisions are based on the maintenance history (e.g., replacement history) of the devices as well as the past write history.

Abstract: A system and method that provides users of network data storage systems with the ability to gain the advantages of a clustered storage server system, in which volumes stored on multiple server nodes are linked into a virtual global hierarchical namespace, without first having to migrate their data to the clustered storage server system. The system employs an extended virtual global hierarchical namespace that allows client systems to access, via the extended global namespace, volumes stored on the clustered storage server system and on one or more storage servers that are remote from and do not constitute a part of the clustered system. The extended global namespace can also be employed to perform migration of volume data among the multiple nodes of the clustered storage server system and the remote storage servers.

Abstract: A system and method that provides users of network data storage systems with the ability to gain the advantages of a clustered storage server system, in which volumes stored on multiple server nodes are linked into a virtual global hierarchical namespace, without first having to migrate their data to the clustered storage server system. The system employs an extended virtual global hierarchical namespace that allows client systems to access, via the extended global namespace, volumes stored on the clustered storage server system and on one or more storage servers that are remote from and do not constitute a part of the clustered system. The extended global namespace can also be employed to perform migration of volume data among the multiple nodes of the clustered storage server system and the remote storage servers.