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A system and method to allow a volume to appear in multiple locations in a super-namespace. A super-namespace is a hierarchy of namespaces within a storage system environment, such as a storage system cluster. The volume can appear in multiple locations in the super-namespace and/or in multiple name

A system and method to allow a volume to appear in multiple locations in a super-namespace. A super-namespace is a hierarchy of namespaces within a storage system environment, such as a storage system cluster. The volume can appear in multiple locations in the super-namespace and/or in multiple namespaces within the super-namespace.

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1. A method, comprising: creating a volume on a computer storage device in a namespace environment with a hierarchy of multiple namespaces including a trunk namespace;generating a plurality of instantiations of the volume in the namespace environment;maintaining a junction table having a plurality o

1. A method, comprising: creating a volume on a computer storage device in a namespace environment with a hierarchy of multiple namespaces including a trunk namespace;generating a plurality of instantiations of the volume in the namespace environment;maintaining a junction table having a plurality of entries;associating, in a first entry of the junction table, a first instantiation of the volume with a parent namespace having a parent namespace identifier and a first child namespace having a first child namespace identifier, wherein the namespace environment with the hierarchy of multiple namespaces includes the parent namespace and first child namespace;associating, in a second entry of the junction table, a second instantiation of the volume with the parent namespace having the parent namespace identifier and a second child namespace having a second child namespace identifier, thereby having the first and second instantiations of the volume appear in multiple namespaces in the namespace environment with the hierarchy of multiple namespaces that include the second child namespace; andstoring, in the junction table having the plurality of entries, restricting values of namespace identifiers such that an instantiation of the volume cannot become its own ancestor within the hierarchy of multiple namespaces, wherein the restricting values require that if the instantiation of the volume is in the trunk namespace, the parent namespace identifier and child namespace identifier for the instantiation of the volume equal a trunk namespace identifier of the trunk namespace. 2. The method of claim 1 comprising: mounting a child data container in the hierarchy of multiple namespaces, wherein the child data container is related to a parent data container;generating a junction-type inode for the child data container, the junction-type inode comprising an inode number and a generation number;generating a particular junction table entry referenced by the inode number, the generation number, a parent data container identifier, and the parent namespace identifier; andstoring, in the particular junction table entry, a particular child namespace to identifier and a child data container identifier corresponding to the child data container. 3. The method of claim 1 comprising: mounting a parent data container in the hierarchy of multiple namespaces wherein the parent data container is related to a child data container;generating a junction-type inode for the parent data container, the junction-type inode comprising an inode number and a generation number;generating a particular junction table entry referenced by the inode number, the generation number, a child data container identifier, and the particular child namespace identifier; andstoring, in the junction table entry, the parent namespace identifier and a parent data container identifier corresponding to the parent data container. 4. The method of claim 1 wherein a master set identifier identifies the volume. 5. The method of claim 1 wherein the junction table is replicated across a cluster of volumes. 6. The method of claim 1, further comprising: accessing a selected instantiation of the volume in the hierarchy of multiple namespaces by receiving a file handle for a data access operation, wherein the file handle comprises a namespace identifier of the selected instantiation of the volume and a volume identifier of the selected instantiation of the volume; andsearching the junction table for a junction table entry with the namespace identifier and the volume identifier. 7. The method of claim 1 wherein the hierarchy of namespaces is organized as a tree structure with the trunk namespace and one or more branch namespaces associated with the trunk namespace. 8. The method of claim 1 wherein the restricting values require child namespace identifier that is equal to a branch namespace also have the parent namespace identifier that is equal to the trunk namespace identifier of the trunk namespace. 9. A system, comprising: a volume on a computer storage device configured to be created in a namespace environment with a hierarchy of multiple namespaces including a trunk namespace;a first entry in a junction table associated with the volume, the first entry including a parent namespace identifier identifying a parent namespace of the namespace environment and a first child namespace identifier identifying a first child namespace of the namespace environment;a second entry in the junction table associated with the volume, the second entry including the parent namespace identifier identifying the parent namespace and a second child namespace identifier identifying a second child namespace of the namespace environment, thereby having the volume appear in at least two namespaces in the namespace environment with the hierarchy of multiple namespaces; anda third entry in the junction table storing a restricting value of a namespace identifier whereby the volume cannot become its own ancestor within the hierarchy of multiple namespaces, wherein the restricting values requires that if the first child namespace identifier or the second child namespace identifier is equal to a branch namespace, the parent namespace identifier that identifies the parent namespace is to equal a trunk namespace identifier of the trunk namespace. 10. The system of claim 9 comprising: a child data container configured to be created in the hierarchy of multiple namespaces, wherein the child data container is configured to relate to a parent data container;a junction-type inode of the child data container, the junction-type inode comprising an inode number and a generation number;a particular junction table entry configured to be referenced by the inode number, the generation number, a parent data container identifier corresponding to the parent data container, and the parent namespace identifier; andthe particular junction table entry further configured to reference a particular child namespace identifier and a child data container identifier corresponding to the child data container. 11. The system of claim 9 comprising: a parent data container configured to be mounted in the hierarchy of multiple namespaces, wherein the parent data container is related to a child data container;a junction-type inode for the parent data container, the junction-type inode comprising an inode number and a generation number;a particular junction table entry configured to be referenced by the inode number, the generation number, a child data container identifier corresponding to the child data container, and a particular child namespace identifier; andthe particular junction table entry further configured to reference the parent namespace identifier and a parent data container identifier corresponding to the parent data container. 12. The system of claim 9 wherein a master set identifier identifies the volume. 13. The system of claim 9 wherein the junction table is replicated across a cluster of volumes. 14. The system of claim 9, further comprising: a file handle configured to be used in accessing a selected volume in the hierarchy of multiple namespaces, wherein the file handle comprises a particular namespace identifier of the selected volume and a volume identifier of the selected volume, and wherein the junction table is further configured to be searched for a junction table entry with the particular namespace identifier and the volume identifier. 15. The system of claim 9 wherein the hierarchy of namespaces is configured to be organized as a tree structure with the trunk namespace and one or more branch namespaces associated with the trunk namespace. 16. The system of claim 9 wherein the restricted values require a selected volume in the trunk namespace to have the parent namespace identifier and child namespace identifier equal to the trunk namespace identifier of the trunk namespace. 17. A non-transitory computer readable storage medium containing executable program instructions executed by a processor, comprising: program instructions that create a volume on a computer storage device in a namespace environment with a hierarchy of multiple namespaces having a trunk namespace;program instructions that maintain a plurality of entries in a junction table;program instructions that associate the volume with a parent namespace, of the namespace environment, having a parent namespace identifier and a first child namespace, of the namespace environment, having a first child namespace identifier in a first entry of the junction table;program instructions that associate the volume with the parent namespace having the parent namespace identifier and a second child namespace, of the namespace environment, having a second child namespace identifier in a second entry of the junction table, thereby having the volume appear in multiple namespaces in the namespace environment with the hierarchy of multiple namespaces; andprogram instructions that store, in the junction table having the plurality of entries, restricting values of namespace identifiers such that the volume cannot become its own ancestor within the hierarchy of multiple namespaces, wherein the restricting values require that if the volume is in the trunk namespace, the parent namespace identifier and child namespace identifier for the volume equal a trunk namespace identifier of the trunk namespace.