Abstract: Example implementations relate to metadata operations in a storage system. An example includes receiving, by a storage controller of a deduplication storage system, a plurality of data streams to be stored in persistent storage of the deduplication storage system; identifying, by the storage controller, a set of journals in a first journal group that are modified during a first backup process; determining, by the storage controller, a count of the set of journals that are modified during the first backup process; comparing, by the storage controller, the determined count to a migration threshold; and migrating, by the storage controller, at least one journal of the set of journals to a second journal group based at least on a comparison of the determined count to the migration threshold.

Abstract: Example implementations relate to deduplication operations in a storage system. An example includes, in response to initiation of a new backup process to store a first stream of data, initializing a temporary sparse index to be stored in a memory of a deduplication storage system; identifying a cloned portion of the first data stream; identifying at least one container index associated with the cloned portion of the first data stream; identifying a set of hook points included in the at least one container index; and populating the temporary sparse index with a set of entries, the set of entries mapping the identified set of hook points to the at least one container index.

Abstract: Example implementations relate to data storage. An example includes a method comprising: receiving a data stream to be stored in a persistent storage of a deduplication storage system; assigning new data units to container indexes; storing the new data units of the data stream in a plurality of intake buffers, where each new data unit is stored in the intake buffer associated with the container index it is assigned to; determining whether a cumulative amount stored in the plurality of intake buffers exceeds a first threshold; in response to a determination that the cumulative amount exceeds the first threshold, determining a least recently updated intake buffer of the plurality of intake buffers; generating a first container entity group object comprising a set of data units stored in the least recently updated intake buffer; and writing the first container entity group object from memory to the persistent storage.

Abstract: Example implementations relate to metadata operations in a storage system. An example includes generating, by a storage controller of a deduplication storage system, a candidate list of container indexes for matching operations of a received data segment, each container index in the candidate list having an associated match cost; identifying, by the storage controller, a journal group associated with a first container index listed in the candidate list; reducing, by the storage controller, a match cost associated with the first container index in response to a determination that the identified journal group is in a modified state; and performing, by the storage controller, the matching operations of the received data segment based at least on the reduced match cost of the first container index.

Abstract: Example implementations relate to metadata operations in a storage system. An example includes receiving, by a storage controller of a deduplication storage system, a plurality of data streams to be stored in persistent storage of the deduplication storage system; identifying, by the storage controller, a set of journals in a first journal group that are modified during a first backup process; determining, by the storage controller, a count of the set of journals that are modified during the first backup process; comparing, by the storage controller, the determined count to a migration threshold; and migrating, by the storage controller, at least one journal of the set of journals to a second journal group based at least on a comparison of the determined count to the migration threshold.

Abstract: Example implementations relate to metadata operations in a storage system. An example storage system includes a machine-readable storage storing instructions executable by a processor to determine to generate a synthetic full backup based on data stream representations of a plurality of data streams. The instructions are also executable to, in response to a determination to generate the synthetic full backup, create a logical group including the data stream representations. The instructions are also executable to specify a cache resource allocation for the logical group, and generate the synthetic full backup from data stream representations using an amount of a cache resource limited by the cache resource allocation for the logical group.

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: 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: Example implementations relate to metadata operations in a storage system. An example includes a machine-readable medium storing instructions that upon execution cause a processor to: receive a data stream to be stored in persistent storage of a deduplication storage system; store data units of the data stream in a container entity group object according to arrival time, where the data units of the container entity group object are referenced by a plurality of container indexes; generate a data index to list each container index that references at least one data unit included in the container entity group object; and in response to a determination that the total size of the container entity group object exceeds the threshold size, transfer the container entity group object from memory to the persistent storage.

Abstract: Example implementations relate to metadata operations in a storage system. An example includes detecting, by a storage controller of a deduplication storage system, a housekeeping operation to perform updates to data of a set of container indexes of stored deduplicated data; in response to a detection of the housekeeping operation, the storage controller identifying, among the set of container indexes, a plurality of container indexes associated with a particular journal group, the particular journal group comprising a plurality of journals to store updates to data of the plurality of container indexes, respectively; and maintaining, by the storage controller, the particular journal group loaded in memory until all of the updates of the housekeeping operation to the plurality of container indexes have been stored in the respective journals of the particular journal group.

Abstract: Examples may include storage of a small object representation in a deduplication system. Examples may store the small object representation of an object in the deduplication system based on a determination that the object is smaller than a threshold size. In examples, the small object representation may include a direct reference from a top-level data structure to small object metadata in a bottom-level data structure of the small object representation.

Abstract: Example implementations relate to metadata operations in a storage system. An example storage system includes a machine-readable storage storing instructions executable by a processor to determine to generate a synthetic full backup based on data stream representations of a plurality of data streams. The instructions are also executable to, in response to a determination to generate the synthetic full backup, create a logical group including the data stream representations. The instructions are also executable to specify a cache resource allocation for the logical group, and generate the synthetic full backup from data stream representations using an amount of a cache resource limited by the cache resource allocation for the logical group.

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: 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 journals for metadata changes. An example includes detecting, by a storage controller of a deduplication storage system, a cloning operation of a manifest range; loading a journal from persistent storage into memory in response to the detected cloning operation, wherein the journal is to store changes to a container index associated with the manifest range, and wherein the container index is not loaded into the memory in response to the detected cloning operation; and updating the journal in the memory to include an indication of changes to metadata of the container index that is not loaded into the memory, wherein the changes to the metadata are associated with the detected cloning operation.

Abstract: Examples may include storage of a small object representation in a deduplication system. Examples may store the small object representation of an object in the deduplication system based on a determination that the object is smaller than a threshold size. In examples, the small object representation may include a direct reference from a top-level data structure to small object metadata in a bottom-level data structure of the small object representation.

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: 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.