Emc IP Holding Company LLC

Dell Products Inc.

Rohit K Chawla

Ahsan Rashid

Philippe Armangau

Alexander S Mathews

Soumyadeep Sen

Dixitkumar Vishnubhai Patel

Marc A De Souter

Morgan A Clark

Kumari Bijayalaxmi Nanda

Jean-Pierre Bono

William C Davenport

Feng Zhang

Gaurav Chawla

Gary Benedict Kotzur

Farzad Khosrowpour

Ivan Basov

Vamsi K Vankamamidi

Kevin Thomas Marks

Jacob Cherian

Walter Forrester

Richard P Ruef

Ye Zhang

Stephen Gouze Luning

Michal Marko

Ahmad Hassan Tawil

Ahmad A J Ali

Michael Scheer

Hao Pan

Diane Delgado

Howard A Shoobe

Bijayalaxmi Nanda

A method facilitating an update to a file system comprises storing a set of transaction log entries at log space of a storage log associated with the file system, the transaction log entries comprising instructions for fulfilling a set of transactions that define change to the file system, assigning, in an ordered sequence corresponding to a sequence order of journalling of the set of transaction log entries to the log space, transaction markers to a set of transaction marker lists, wherein the transaction markers reference the set of transaction log entries, and, for individual transaction markers of the transaction markers, preventing reuse of the log space corresponding thereto until an evaluation of the set of transaction marker lists results in a determination that writing of all modified system metadata corresponding thereto has been executed and that the transaction marker is set equal to a global head transitioning the transaction markers.

Multiple bitmap single head/tail retirement transaction order

Described is technology that facilitates journalling a transaction log entry to chunks of storage while allowing for obtaining of modified system metadata associated therewith in the case of a computing device issue. An associated method comprises at least storing, by a system operatively coupled to a processor, a set of transaction log entries at log space of a storage log associated with a file system, wherein the transaction log entries comprise instructions for fulfilling a set of transactions, and wherein the transactions define changes to the file system, generating a checkpoint marker corresponding to a set of log storage objects of the storage log at which the transaction log entries are stored, and based on the checkpoint marker, preventing, by the system, reuse of the log space until writing of all modified system metadata corresponding to the transaction log entries has been executed.

Multi-log checkpoint-based retirement transaction order in multi-chunk log

Techniques for performing processing to recover metadata may include: shadow top structures, and performing processing that uses the shadow top structures to recover information for an index node associated with an object of a file system having a file system logical address space. One of the shadow top structures is created for each metadata (MD) top node of a MD mapping structure used to determine storage locations of data stored at corresponding logical addresses in the file system logical address space. Each MD top node is used in determining storage locations for a specified subrange of logical addresses of the file system logical address space. Each shadow top structure corresponding to a MD top node describes each file system object mapped to a logical address included in the specified subrange of logical addresses of the file system address space associated with the corresponding MD top node.

Techniques for duplicating inode state to prevent loss of inode metadata

Described is a technology that facilitates directory level snapshots at any level of a filesystem's namespace. A directory inode mapping file associates a first directory's virtual inode number(s) with real inode number(s). A snapshot of the first directory creates a second directory with a second directory inode mapping file copied from the first directory inode mapping file, thereby sharing the real inode data structure(s) of the first directory. In the event that one of the directories is to be modified, the directory real inode is split to provide a new directory real inode file for the to-be-modified directory, with the modification after the split.

Directory snapshots based on directory level inode virtualization

The technology described herein efficiently determines whether a real inode is shared among views, or owned. In-memory data structures include a view snapshot generation counter that is increased as a snapshot that generates a view is created, and an inode total weight. An in-memory virtual inode cache dataset for a filesystem object associated with the view is instantiated with the value of snapshot generation counter, sharing-related data based on the inode mapping file entry for the object, and an inode access weight. To determine whether the inode is shared (and needs to be split), such as on a write to the object, the in-memory data is evaluated. The real inode is shared if the generation counters are unequal, if the sharing-related data indicates sharing at an intermediate indirect block level, or indicates sharing at the inode level and the inode access weight is less than the inode total weight.

Determining a sharing relationship of a file in namespace snapshots

Described is hard link handling when a directory snapshot exists that includes the hard link's connected file object. A hard link is created by allocating a virtual inode number for the hard link, with the virtual inode number mapped to a real inode number that identifies a real inode of the file object; the hard link is assigned weight. A total weight associated with the real inode is increased by the hard link weight, and a hard link data store is updated with an entry for the hard link. Upon receiving data write request to the hard link, weight data determines that the file object is shared as a result of the snapshot; the hard link is disassociated from the real inode file, and associated with a new real inode number and new real inode of a new file object. The data is written based on the new real inode.

Hard link handling with directory snapshots

A method, computer program product, and computer system for maintaining a back pointer from a physical layer block (PLB) to a virtual layer block (VLB) in a multi-level hierarchical file system. A generation number may be maintained in the VLB, wherein the generation number may indicate when data is moved from the PLB to another PLB. An object may be reconstructed in the multi-level hierarchical file system based upon, at least in part, at least one of the back pointer and the generation number.

System and method for inline recovery of a file system resource allocator

Technology described herein can perform deletion of a snapshot or portion thereof. In an embodiment, a system can comprise a processor and a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations. The operations can comprise, to delete a snapshot, or a portion of a snapshot, of a real filesystem, reading an inode mapping file (IMF) of the snapshot that indexes a virtual inode number (VIN) corresponding to a real inode. The operations further can comprise identifying the real inode of the snapshot referenced by the VIN, identifying a file object corresponding to the real inode, and deleting the file object from the snapshot.

Deletion of snapshot of filesystem

Techniques for providing lifecycle handling of faults associated with a storage appliance. The techniques can include recording information or details of one or more detected faults associated with a storage appliance in a fault database, analyzing the recorded fault information/details by an analytic tool, and determining whether to perform immediate recovery or defer recovery of the detected fault(s) based at least on a recommendation of the analytic tool. In this way, taking the storage appliance offline upon occurrence of a single fault can, for the most part, be avoided. In addition, because the detection of faults is not performed within a fault domain for a filesystem handling files for a single or limited number of volume families, a deduplication domain for the files of the filesystem is not restricted to the single or limited number of volume families.

Lifecycle of handling faults in next generation storage systems

An apparatus comprises a processing device configured to identify faults associated with a logical address space in a fault domain of a storage system, the faults specifying fault reason codes and metadata types for logical pages in the logical address space associated with the faults. The processing device is also configured to determine a fault summary characterizing impact of the faults in the fault domain of the storage system, the fault summary being based on aggregating fault scores assigned to the fault reason codes and the metadata types specified in the faults. The processing device is further configured to generate a recommendation on whether to initiate recovery of the fault domain of the storage system based on the fault summary, and to initiate recovery of the fault domain of the storage system based on the generated recommendation.

Generating recommendations for initiating recovery of a fault domain representing logical address space of a storage system

An apparatus includes a processing device configured to generate log records each representing a pointer from a leaf page in a logical address space of a storage system to a virtual block address and comprising a leaf page address of the leaf page. The processing device is also configured to identifying a subset of the log records representing pointers to a given virtual block address to determine a first reference count, and to determine whether the first reference count is different than a second reference count obtained from a given virtual entry of a given virtual block structure that corresponds to the given virtual block address. The processing device is further configured, responsive to determining that the first and second reference counts are different, to modify pointers to the given virtual block address in leaf pages with associated leaf page addresses in the identified subset of the log records.

Mapping virtual block addresses to portions of a logical address space that point to the virtual block addresses

A method of repairing an indirect addressing structure of a file system damaged by corruption of a virtual data block (VDB) mapping data stored in corresponding physical data blocks (PDBs) includes scanning PDB descriptors to identify PDBs storing data mapped by the corrupted VDB, where each identified PDB includes a set of PDB entries each having a backward pointer identifying a corresponding VDB entry of a corresponding VDB. The identified PDBs are scanned to identify PDB entries whose backward pointers refer to VDB entries of the corrupted VDB, then a replacement VDB is created by (1) for each of the identified PDB entries, recreating a corresponding VDB entry including a forward pointer to the identified PDB entry, and (2) incorporating the recreated VDB entries into the replacement VDB. The replacement VDB is then incorporated into the indirect addressing structure in place of the corrupted VDB.

Data storage system with repair of virtual data blocks of internal file system

A technique for repairing an indirect addressing structure of a file system damaged by corruption of a mid-level mapping (MID) page includes scanning selected leaf pages to identify leaf pages associated with the corrupted MID page, then recreating the MID page by recreating pointers to the identified leaf pages. The scanning includes (1) based on an association of groups of leaf pages with corresponding sets of families of storage objects, scanning the leaf pages of only those groups of leaf pages associated with the family of storage objects for the corrupted MID page. The scanning further includes (2) performing a two-pass process including first identifying all leaf pages for the logical offset range of the corrupted MID page and then pruning those identified leaf pages that are reachable via non-corrupted MID pages, yielding the leaf pages for the corrupted MID page only, usable to recreate the corrupted MID page.

Data storage system with repair of mid-level mapping blocks of internal file system

Techniques for handling pattern identifiers in a data storage system. By replacing a block pointer with a pattern identifier, the techniques can identify a data block (or an indirect data block) as a bad block, without resorting to the use of a separate flag or bad block (BB) bit in per-block metadata (e.g., a mapping pointer) of the data block. The techniques can also avoid waste of valuable metadata space by using pattern identifiers at various levels of a mapping tree, leveraging pointer granularity at lower levels, mid-levels, and progressively higher levels of the mapping tree.

Handling pattern identifiers in a data storage system

An in-line (or foreground) approach to obtaining contiguous ranges of free space in a file system of a data storage system that can select windows having blocks suitable for relocation at a time when one or more blocks within the respective windows are freed or de-allocated. By providing the in-line or foreground approach to obtaining contiguous ranges of free space in a file system, a more efficient determination of windows having blocks suitable for relocation can be achieved, thereby conserving processing resources of the data storage system.

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Scotch Plains, NJ, United States of America

Rohit K Chawla