Storage system capable of managing a plurality of snapshot families and method of operating thereof

A storage system comprising a control layer with a cache memory, the control layer configured to manage a plurality of snapshot families, each family constituted by snapshot family (SF) members having hierarchical relations therebetween, wherein the control layer is further configured:

• to identify, upon receiving a read request specifying logical unit number (LUN) of an addressed logical volume and addressed logical block address (LBA) therein, an addressed snapshot family and an addressed SF member therein corresponding to the addressed LUN;
• to search the cache memory for an addressed data block corresponding to the addressed LBA and associated with the addressed snapshot family and the addressed SF member;
• in a case of missing the addressed data block in the cache memory, to identify in the cache memory all dirty data blocks corresponding to the addressed LBA and associated with the addressed snapshot family, thus giving rise to candidate data blocks;
• to identify for the addressed snapshot family an SF member representing, upon virtual destaging all candidate data blocks, the addressed LBA in a mapping data structure, thus giving rise to a destage owner,
• wherein the mapping data structure is configured to provide mapping between a given LBA and one or more physical addresses corresponding to SF members such that a given physical address is represented by one and only one SF member among SF members sharing the given physical address;
• and
• in a case when the identified destage owner is associated with a candidate data block, to read from the cache memory such candidate data block.

A non-transitory computer readable storage medium comprising computer readable program code embodied therein for operating a storage system comprising a control layer with a cache memory, the control layer operable to manage a plurality of snapshot families, each family constituted by snapshot family (SF) members having hierarchical relations therebetween, the computer readable program code causing the control layer:

• upon receiving a read request specifying logical unit number (LUN) of an addressed logical volume and addressed logical block address (LBA) therein,
• to identify an addressed snapshot family and an addressed SF member therein corresponding to the addressed LUN;
• to search the cache memory for an addressed data block corresponding to the addressed LBA and associated with the addressed snapshot family and the addressed SF member;
• in a case of missing the addressed data block in the cache memory, to identify in the cache memory all dirty data blocks corresponding to the addressed LBA and associated with the addressed snapshot family, thus giving rise to candidate data blocks;
• to identify for the addressed snapshot family an SF member representing, upon virtual destaging all candidate data blocks, the addressed LBA in a mapping data structure, thus giving rise to a destage owner,
• wherein the mapping data structure is configured to provide mapping between a given LBA and one or more physical addresses corresponding to SF members such that a given physical address is represented by one and only one SF member among SF members sharing the given physical address;
• and
• in a case when the identified destage owner is associated with a candidate data block, to read from the cache memory such candidate data block.

A method of operating a storage system comprising a control layer with a cache memory, the control layer operable to manage a plurality of snapshot families, each family constituted by snapshot family (SF) members having hierarchical relations therebetween, the method comprising:

• upon receiving a read request, the control layer
• searching the cache memory for an addressed data block corresponding to LBA addressed in the read request and associated with snapshot family and the SF member corresponding to the read request;
• in a case of missing the addressed data block in the cache memory, identifying in the cache memory all dirty data blocks corresponding to the addressed LBA and associated with the addressed snapshot family, thus giving rise to candidate data blocks;
• identifying among SF members of the addressed snapshot family a destage owner;
• and
• in a case when the identified destage owner is associated with a candidate data block, reading from the cache memory such candidate data block.