Abstract: Example implementations relate to metadata operations in a storage system. An example includes a storage controller loading a manifest from persistent storage into memory, and loading a first container index from persistent storage into the memory. The first container index is associated with the manifest loaded into the memory. The storage controller determines whether a tracking data structure of the first container index includes an identifier of the manifest. In response to a determination that the tracking data structure of the first container index does not include the identifier of the manifest, the storage controller discards the manifest.

Abstract: Example implementations relate to metadata operations in a storage system. An example method includes receiving, from a first stream process, a first write request for a first container index in memory. The method further includes, in response to a receipt of the first write request, sending a first token to the first stream process without writing the first container index to a persistent storage. The method further includes receiving, from a second stream process, a first completion request for the first container index. The method further includes, in response to a receipt of the first completion request, writing the first container index from the memory to the persistent storage.

Abstract: Example implementations relate to storing manifest portions in a metadata cache. An example includes receiving, by a storage controller, a read request associated with a first data unit. In response to receiving the read request, the storage controller stores a manifest portion in a metadata cache, the stored manifest portion comprising a plurality of records, the plurality of records including a first record associated with the first data unit. The storage controller determines storage information of the first data unit using pointer information included in the first record of the stored manifest portion, and replaces the pointer information in the first record with the determined storage information of the first data unit.

Abstract: Examples implementations relate to journals for metadata changes. An example includes detecting, by a storage controller, metadata changes associated with a container index of a deduplication storage system; recording, by the storage controller, the detected metadata changes in a journal associated with the container index, where the journal is included in a journal group comprising a plurality of journals; determining, by the storage controller, whether a filled amount of the journal exceeds a fill threshold; and, in response to a determination that the filled amount of the journal does not exceed the fill threshold, writing the journal group from memory to persistent storage.

Abstract: In some examples, in response to an event at the deduplication system, a system accesses item metadata of a backup item that is backed up to a remote object storage system, the item metadata of the backup item including range information indicating a range of identifier values for portion objects of the backup item stored in the remote object storage system. The system issues, based on the range information, requests to obtain respective attribute information of the portion objects of the backup item stored in the remote object storage system. The system determines, based on the attribute information, a name of a given portion object of the backup item already used.

Abstract: Examples include selection of a remote object storage system for a deduplication data item. Some examples may include determination of an expected usage frequency for the deduplication data item, selection of a remote object cloud storage system based on the expected usage frequency for the data item, and provision of the deduplication data item to the selected remote object storage system for storage as an object in the selected remote object storage system.

Abstract: In one example, a processor executes computer-readable instructions that cause the processor to: for each of a plurality of buckets of a data structure stored in a cache of a computer system, execute a first thread such that: a plurality of entries stored in the bucket are inspected to identify a respective entry for removal from the cache based on respective usage metrics of the entries of the bucket, wherein each entry comprises a container of data chunks, access is restricted to the bucket by at least a second thread during the inspection of the respective entries from the bucket by the first thread, one entry of the identified entries is selected for removal from the cache based on a comparison between the respective usage metrics of the identified entries, and the processor enables concurrent access to the plurality of buckets by multiple threads requesting access to the cache, whereby a thread can access and inspect one of the buckets and, during the inspecting, at least one other thread can access anot

Abstract: In some examples, region cloning may include obtaining a clone request to clone a logical range of a source backup. The clone request may specify the source backup, a logical start offset, and a logical end offset. A source manifest associated with the logical range of the source backup may be determined. A start entry of the source manifest may be identified based on the logical start offset. The start entry may represent a start data chunk. A determination may be made as to whether the logical start offset represents an intermediate position of the start data chunk, and if so, a start partial chunk entry representing a sub-range of the start data chunk may be appended to a destination manifest. A backup of the logical range of the source backup may be generated based on the destination manifest with the appended start partial chunk entry.

Abstract: In some examples, region cloning may include obtaining a clone request to clone a logical range of a source backup. The clone request may specify the source backup, a logical start offset, and a logical end offset. A source manifest associated with the logical range of the source backup may be determined. A start entry of the source manifest may be identified based on the logical start offset. The start entry may represent a start data chunk. A determination may be made as to whether the logical start offset represents an intermediate position of the start data chunk, and if so, a start partial chunk entry representing a sub-range of the start data chunk may be appended to a destination manifest. A backup of the logical range of the source backup may be generated based on the destination manifest with the appended start partial chunk entry.

Abstract: Examples include selection of a remote object storage system for a deduplication data item. Some examples may include determination of an expected usage frequency for the deduplication data item, selection of a remote object cloud storage system based on the expected usage frequency for the data item, and provision of the deduplication data item to the selected remote object storage system for storage as an object in the selected remote object storage system.

Abstract: Examples include application of a variable-sized content-defined chunking technique to a first data portion to identify a content-defined chunk boundary at least partially defining a remainder section, merging of the remainder section with a second data portion ordered before the first data portion to create a merged section, and application of the chunking technique to the merged section.

Abstract: Examples include the acquisition of objects names for portion index objects. Some examples include acquisition, from a remote object storage system, of a list of object names for a plurality of portion index objects, stored in the remote object storage system. In some examples, for each of the portion index objects, the acquired object name includes an identifier of an associated deduplicated backup item and information identifying a data range of the associated deduplicated backup item that is represented by metadata of the portion index object.

Abstract: In some examples, in response to an event at the deduplication system, a system accesses item metadata of a backup item that is backed up to a remote object storage system, the item metadata of the backup item including range information indicating a range of identifier values for portion objects of the backup item stored in the remote object storage system. The system issues, based on the range information, requests to obtain respective attribute information of the portion objects of the backup item stored in the remote object storage system. The system determines, based on the attribute information, a name of a given portion object of the backup item already used.

Abstract: Examples include the acquisition of objects names for portion index objects. Some examples include acquisition, from a remote object storage system, of a list of object names for a plurality of portion index objects, stored in the remote object storage system. In some examples, for each of the portion index objects, the acquired object name includes an identifier of an associated deduplicated backup item and information identifying a data range of the associated deduplicated backup item that is represented by metadata of the portion index object.

Abstract: Examples include splitting a non-leaf node of a directed acyclic graph (DAG) in response to determinations that a content-defined fingerprint of a data portion is a breakpoint value and that a target insertion point is between two leaf nodes having a common non-leaf node parent, and determination of whether the data portion was previously stored in a backup system based on the DAG.

Abstract: Examples include application of a variable-sized content-defined chunking technique to a first data portion to identify a content-defined chunk boundary at least partially defining a remainder section, merging of the remainder section with a second data portion ordered before the first data portion to create a merged section, and application of the chunking technique to the merged section.