Emc IP Holding Company LLC

Vmware, Inc.

Emc Corporation

Pranay Singh

Wenguang Wang

Pengju Shang

George Mathew

Enning Xiang

Englin Koay

Abhay Kumar Jain

Dhawal Bhagwat

Nitin Rastogi

Subhradyuti Sarkar

Richard Paul Spillane

Murthy V Mamidi

Sriram Patil

Robert L Fair

Junlong Gao

Hardik Singh Negi

Long Yang

Imran Khan

Hemant P Khachane

Sai Chivukula

Fan Ni

Srikanta Shivanna

A method for resumeable snapshot deletion is provided. A method for deletion of nodes maintained in an ordered data structure for a first snapshot includes processing the nodes maintained in the ordered data structure according to a defined order, setting a node path cursor with a pointer to a node and an indication of the deletion of the node; storing the node path cursor in a persistent storage; and during processing of the nodes: detecting a failure; after the failure, checking the pointer of the node path cursor; and resuming processing of the nodes starting from the first node indicated by the pointer.

Resumable copy-on-write (COW) B+tree pages deletion

Techniques for efficiently managing a file clone from a filesystem which supports efficient volume snapshots are provided. In some embodiments, a system may receive an instruction to remove the file clone from the filesystem. The file clone may be a point-in-time copy of metadata of an original file. The system may further&#x2014;for a file map entry in a filesystem tree associated with the file clone, the file map entry indicating a data block&#x2014;decrement a reference count in a reference count entry associated with the file map entry. The reference count entry may be stored in the filesystem tree according to a key and the key may comprise an identification of the original file. The system may further reclaim the data block in a storage system when the reference count is zero.

Embedded reference counts for file clones

The present disclosure is related to methods, systems, and machine-readable media for managing extent sharing between snapshots using mapping addresses. A first mapping address can be assigned to a first extent responsive to a request to write the first extent. A second mapping address can be assigned to a second extent responsive to a request to write the second extent. A snapshot can be created. A snapshot mapping address, that is monotonically increased from the second mapping address, can be assigned to the snapshot. A third mapping address, that is monotonically increased from the second mapping address, can be assigned to a third extent of the snapshot responsive to a request to write the third extent. An ownership status of each of the first extent, the second extent, and the third extent can be determined based respectively on: a comparison between the first mapping address and the snapshot mapping address, a comparison between the second mapping address and the snapshot mapping address, and a comparison between the third mapping address and the snapshot mapping address.

Managing extent sharing between snapshots using mapping addresses

In one example, a method for writing data includes receiving a write request and performing a first type of logging process in connection with the write request, and creating a corresponding first logging record. Additionally, a second type of logging process is performed in connection with the write request, and a corresponding second logging record created, where the second type of logging process is different from the first type of logging process. Next, a determination is made, as between the two logging records, which of the logging records requires the least amount of non-volatile random access memory (NVRAM), and the logging record that requires the least amount of NVRAM is written to the NVRAM.

Hybrid NVRAM logging in filesystem namespace

A method for deleting one or more snapshots using micro-batch processing is provided. The method includes receiving a request to delete the one or more snapshots, identifying one or more middle map extents exclusively owned by the one or more snapshots requested to be deleted, wherein metadata for the one or more snapshots is stored in one or more logical maps having logical map extents mapping logical block addresses (LBAs) to middle block addresses (MBAs) and a middle map having middle map extents mapping MBAs to physical block addresses (PBAs) of physical locations where data blocks are written, adding MBAs of the identified one or more middle map extents in a batch, determining a first micro-batch including a first subset of the MBAs in the batch, the first subset of MBAs being MBAs less than a first upper bound MBA, and using a first transaction to delete the middle map extents corresponding to the first subset of MBAs included in the first micro-batch.

Micro-batching metadata updates to reduce transaction journal overhead during snapshot deletion

A method for the reverse deletion of a plurality of snapshots in a chain of snapshots is provided. The method includes in reverse order, starting from a latest snapshot in time to an earliest snapshot in time of the plurality of snapshots: identifying at least one of a first set of one or more data blocks of a snapshot that are shared with an earlier snapshot in time in the chain of snapshots or a second set of one or more data blocks of the snapshot that are owned by the snapshot and processing the second set of one or more data blocks and skipping processing the first set of one or more data blocks, wherein processing the second set of one or more data blocks comprises performing one or more actions to maintain and/or delete data blocks of the second set of one or more data blocks.

Reverse deletion of a chain of snapshots

System and method for managing copy-on-write (COW) B tree structures for metadata of storage objects stored in a storage system determine, when a request to modify a target storage object stored in the storage system that requires a modification of a target leaf node in a B tree structure for metadata of the target storage object is received, whether an operation sequence number of the target leaf node is greater than a snapshot sequence number of a parent snapshot of a running point of the B tree structure. When the operation sequence number is greater than the snapshot sequence number, the target leaf mode is modified in place without copying the target leaf node. When the operation sequence number is not greater than the snapshot sequence number, the target leaf node is copied as a new leaf node for the B tree structure and the new leaf node is modified.

System and method for managing B tree node sharing using operation sequence numbers

The present disclosure is related to methods, systems, and machine-readable media for deleting snapshot pages using sequence numbers and page lookups. A monotonically-increasing sequence number (SN) can be assigned to each created page of a first snapshot of a storage volume. A first snapshot sequence number (snapSN) can be assigned to the first snapshot responsive to a creation of a second snapshot, wherein the first snapSN is equal to a largest SN of the first snapshot. An SN can be assigned to each created page of the second snapshot, wherein a first page of the second snapshot is assigned an SN monotonically increased from the first snapSN. A second snapSN can be assigned to the second snapshot responsive to a creation of a third snapshot, wherein the second snapSN is equal to a largest SN of the second snapshot. An SN can be assigned to each created page of the third snapshot, wherein a first page of the third snapshot is assigned an SN monotonically increased from the second snapSN. A deletion process can be performed in response to receiving a request to delete the second snapshot that includes deleting a particular page of the second snapshot responsive to determining that the particular page is not shared between the second snapshot and the first snapshot or between the second snapshot and the third snapshot.

Deleting snapshot pages using sequence numbers and page lookups

In one set of embodiments, a computer system can periodically run an unmap service configured to scan a subset of bitmaps maintained by a file system of the computer system. As part of scanning each bitmap in the subset, the unmap service can, for each bit in the bitmap: (1) check whether the bit indicates that a corresponding physical block address (PBA) on the storage backend is currently free; (2) upon determining that the bit indicates the PBA is currently free, identify an extent within the bitmap where the PBA resides; (3) check whether an unmap indicator associated with the extent indicates that at least one free PBA in the extent is not currently unmapped in the storage backend; and (4) upon determining that the unmap indicator indicates at least one free PBA in the extent is not currently unmapped in the storage backend, add the PBA to a list of PBAs to be unmapped.

Asynchronous unmap service

According to some embodiment, a storage system selects one or more directories within a file system as candidates for caching based on directory statistics associated with the directories, where each of the directories includes one or more file objects stored in the storage system. For each of the selected directories, the system determines whether the directory is to be cached based on a directory cache policy. The system caches the directory in a cache memory device in response to determining that the directory is to be cached.

Method and system for caching directories in a storage system

Embodiments are described for a method and system for improving B+Tree scan performance by receiving a data access instruction that specifies pages to be accessed in a data store utilizing a B+Tree data structure; defining a read-ahead context comprising an array of page numbers corresponding to the specified pages; loading the read-ahead context array into a read-ahead cache; and reading the first page of the read-ahead context in a synchronous manner, and each of the subsequent pages of the read-ahead context in an asynchronous manner.

Context-based read-ahead for B+ tree data structures in a deduplication system

A small file storage system reduces the cost of storing and reading segmented data in a deduplication storage system. A data-blocking scheme is used to store small files instead of generating different levels of metadata as is done for larger files in deduplication systems. Among other advantages, the data blocking scheme reduces the cost of reading metadata segments from the content store, reduces the cost of index lookup, CM region read and decompression, and the cost of recalling and restoring small files from cloud storage, all of which contribute to better read performance. Other advantages include faster verification of small files, and improvements in small file data locality on disk with larger segment sizes. By eliminating the need to update metadata segments, embodiments of the small file storage system advantageously increase the efficiency of file updates, especially since updates to smaller files are more random in nature.

Growing community of inventors

Cupertino, CA, United States of America

Pranay Singh