Online metadata backup consistency check

A system, comprising:

• a processor;
• and
• a non-volatile memory in operable communication with the processor and storing computer program code that when executed on the processor causes the processor to execute a process operable to perform the operations of:
• configuring a storage system comprising a processor in operable communication with a storage device, the storage system comprising a metadata journal comprising metadata configured to store information associated with at least one change to be made to information stored on the storage device, and the storage device storing therein a plurality of dirty tree (DT) metadata pages, each DT metadata page corresponding to at least a portion of information written to the storage device from the metadata journal;
• reading the plurality of DT metadata pages from the storage device;
• scanning each respective DT metadata page to detect if a respective DT metadata page comprises a respective entry having an invalid snap group identifier (“snap group ID”) associated with the respective entry, where the respective entry is associated with a first offset;
• creating in the metadata journal, for each detected DT metadata page comprising a respective invalid snap group ID, a corresponding new metadata journal entry comprising a fake journal entry, the fake journal entry configured to point to the respective DT metadata page comprising the invalid snap group ID and to point to the same offset as the first offset, wherein the fake journal entry comprises information configured to indicate that the respective offset, of the respective DT metadata page, is nonexistent;
• configuring the corresponding fake journal entry so that, when the metadata journal is destaged to the storage device, the fake journal entry is configured to reset to nonexistent the invalid snap group ID associated with the entry at the first offset at the DT metadata page;
• destaging the metadata journal, including the fake journal entry associated with the first offset, to the storage device;
• reading an old DT page from the metadata journal, the old DT page corresponding to a DT page having a corrupted entry that is associated with the DT metadata page on the storage device having the corrupted entry, the corrupted entry corresponding to the invalid snap group ID, at the first offset, in the DT metadata page on the storage device;
• and
• modifying the old DT page, at the location of the discarded corrupted entry, with the information associated with the fake journal entry;
• and
• discarding the fake journal entry information from the old DT page.

A computer program product including a non-transitory computer readable storage medium having computer program code encoded thereon that when executed on a processor of a computer causes the computer to operate a storage system, the computer program product comprising:

• computer program code for configuring a storage system comprising a processor in operable communication with a storage device, the storage system comprising a metadata journal comprising metadata configured to store information associated with at least one change to be made to information stored on the storage device, and the storage device storing therein a plurality of dirty tree (DT) metadata pages, each DT metadata page corresponding to at least a portion of information written to the storage device from the metadata journal;
• computer program code for reading the plurality of DT metadata pages from the storage device;
• computer program code for scanning each respective DT metadata page to detect if a respective DT metadata page comprises a respective entry, having an invalid snap group identifier (“snap group ID”) associated with the respective entry, where the respective entry is associated with a first offset;
• computer program code for creating in the metadata journal, for each detected DT metadata page comprising a respective invalid snap group ID, a corresponding new metadata journal entry comprising a fake journal entry, the fake journal entry configured to point to the respective DT metadata page comprising the invalid snap group ID and to point to the same offset as the first offset, wherein the fake journal entry comprises information configured to indicate that the respective offset, of the respective DT metadata page, is nonexistent;
• computer program code for configuring the corresponding fake journal entry so that, when the metadata journal is destaged to the storage device, the fake journal entry is configured to reset to nonexistent the invalid snap group ID associated with the entry at the first offset at the DT metadata page;
• computer program code for destaging the metadata journal, including the fake journal entry associated with the first offset, to the storage device;
• reading an old DT page from the metadata journal, the old DT page corresponding to a DT page having a corrupted entry that is associated with the DT metadata page on the storage device having the corrupted entry, the corrupted entry corresponding to the invalid snap group ID, at the first offset, in the DT metadata page on the storage device;
• discarding the corrupted entry from the old DT page;
• modifying the old DT page, at the location of the discarded corrupted entry, with the information associated with the fake journal entry;
• and
• discarding the fake journal entry information from the old DT page.