Emc IP Holding Company LLC

Dell Products Inc.

Emc Holding Company, LLC

Vladimir Shveidel

Lior Kamran

Ronen Gazit

Uri Shabi

Amitai Alkalay

Bar David

Geng Han

Anton Kucherov

Dror Zalstein

Vamsi K Vankamamidi

Alex Soukhman

Oran Asher Baruch

Jenny Derzhavetz

Yousheng Liu

Vladimir Kleiner

Michael Litvak

Jibing Dong

Philip C Love

Ami Sabo

David Meiri

Nimrod Shani

Xiangping Chen

Changyu Feng

Zvi Schneider

Socheavy D Heng

Kirill Shoikhet

Svetlana Kronrod

Shaul Dar

Maor Rahamim

Gajanan S Natu

Leron Fliess

Alexander Shknevsky

David Bernard

Roy Koren

Adi Katzengold

Philippe Armangau

Xinlei Xu

Shaoqin Gong

Jianbin Kang

Christopher Alan Seibel

Felix Shvaiger

Ying Hu

Steven A Morley

Tal Ben-Moshe

Leonid Ravich

Samuel L Mullis, Ii

David Krakov

Shari Vietry

Haiyun Bao

Alexei Kabishcer

Jason E Raff

Christopher A Seibel

Nir Bar Joseph

Christopher J Jones

Liang Huang

Benny Kirenberg

Seman Shen

David Bar

Yair Hershkovitz

Dennis Rusakov

Dafna Levi-Yadgar

Itai Shavit

Jonathan Volij

Daniel Krauthgamer

Gang Han

Aleksey Kabishcher

A technique for managing reference-count decrements (decrefs) includes defining an aggregation domain that includes multiple tablets created at respective points in time, each of the tablets containing multiple sorted buckets arranged in a respective sequence of bucket identifiers that is repeated across all of the tablets, the sorted buckets containing decrefs for respective sets of metadata pages. The technique further includes assigning a decref job to a specified set of bucket identifiers and destaging, by the decref job, multiple decrefs from the tablets to persistent metadata pages, beginning with decrefs in buckets having the specified set of bucket identifiers and proceeding until a target number of decrefs has been destaged.

Managing decref processing from tablets containing sorted buckets

In at least one embodiment, destaging a write of a user data (UD) log may include: performing deduplication that determines content written by the write to a logical address LA is a duplicate of existing content; and establishing mapping information of a chain of metadata (MD) pages mapping LA to a physical address PA storing the existing content, wherein the chain includes a MD leaf page and a VLB (virtual layer block) page. An update of a MD log can update an indirect pointer (IDP) field of a MD leaf entry of the MID leaf page to reference a VLB entry of the VLB page where the VLB entry further includes PA. A second update of the MD log can increment a reference count of the VLB entry. The second update can be recorded blindly in the MD log without reading or accessing the reference count during destaging the write.

Efficient deduplication in a metadata delta log architecture

A method, computer program product, and computing system for receiving a metadata page for storage within a log-structured metadata store. An entry may be generated within a translation table page of a translation table within the log-structured metadata store, wherein each entry of a plurality of entries within the translation table page is associated with a separate metadata page. One or more metadata page deltas for the metadata page may be recorded in the log-structured metadata store. The one or more metadata page deltas for the metadata page may be flushed to a persistent memory storage. In response to flushing the one or more metadata page deltas for the metadata page, the entry within the translation table page that is associated with the metadata page may be updated without accessing any other entry within the translation table page associated with other metadata pages.

System and method for managing metadata access in a log-structured system

In at least one embodiment, processing can include: maintaining a storage object identifier hash table (SOIDHT) that tracks storage object identifiers (IDs) that have been reassigned among storage objects and that have potential outstanding activity associated with storage objects as prior to performing corresponding reassignments; recording, in a user data (UD) log, a UD log entry corresponding to an operation directed to a storage object assigned a storage object ID, wherein the UD log entry includes a first LSN denoting a point in time when the operation is recorded in the UD log; and flushing the UD log. Responsive to determining that the storage object has a corresponding SOIDHT entry, processing can include determining whether the first LSN of the first UD log entry of the operation is less than a second LSN of the corresponding entry of the SOIDHT.

Storage space accounting techniques allowing storage object identifier reuse and reassignment

In at least one embodiment, processing can include: receiving, at a first node of a system, a cross slice border (CSB) I/O with a target location that crosses a CSB between two slices owned by different nodes; adding an entry for the CSB and CSB I/O to a cross border hash table (CBHT) of the first node; acquiring first locks for logical addresses of the first slice owned by the first node; sending a remote procedure call (RPC) to a second node requesting second locks for second logical addresses of the second slice owned by the second node; receiving an RPC reply in response to the RPC; and responsive to receiving an RPC reply indicating the negative acknowledgement, releasing the first locks and removing the entry from the CBHT of the first node.

Techniques for providing I/O atomicity and preventing deadlock for cross slice border I/Os in a distributed storage system

In at least one embodiment, processing can include: receiving metadata updates for MD pages; recording the MD updates for the MD pages in a MD log; and performing a first destaging phase that writes the MD updates from the MD log to a tablet stored on non-volatile storage. The tablet can include a bucket area and an extension area. The bucket area can include buckets each of which is a predetermined bucket size. The first destaging phase can include: writing a portion of the MD updates from the MD log to the bucket area; and writing a second portion of the MD updates from the MD log to the extension area. Each MD update of the second portion can overflow a corresponding one of the buckets which is included in the bucket area and which is associated with one of the MD pages updated by the MD update.

Techniques using a variable size extension area with two phase destaging

In one embodiment, processing can include: receiving, at a first node, a read I/O to read content C1 of logical address LA, wherein the first node does not own LA; and responsive to determining a hash table of the first node does not include a matching entry for LA, performing processing including: sending a request from the first node to a second node that owns LA; sending, to the first node, a response including an address hint for LA and additional address hints for logical addresses, wherein LA and the additional address hints are included in a logical address subrange associated with a single metadata page used in mapping LA and the logical addresses to physical storage locations that store content of LA and the logical addresses; the first node adding entries to the hash table for the additional address hints; and obtaining C1 using the address hint for LA.

Prefetching by logical address owner in response to peer node mapping request

In at least one embodiment, processing can include receiving, at a first node, a read request directed to a logical address LA owned by a second node. The first node can locally cache content and an address hint corresponding to LA. The first node can issue a request to the second node. The request can include a flag to suppress the second node from returning content stored at the target logical address. The first node can receive a response including an address used to read current content of LA1 from back-end non-volatile storage. The first node can determine whether the address matches the address hint cached on the first node. If the first node determines the address and address hint match, the cached content of LA stored on the first node is valid and can be returned in response to the read as current content stored at LA.

Data caching strategies for storage with ownership of logical address slices

Techniques for updating sparse metadata in a metadata delta log (MDL)-based storage system. The techniques include providing a 3-level MDL, which includes a first level for a first set of buckets initially (and temporarily) designated as 'active', a second level for a second set of buckets initially (and temporarily) designated as “de-staging”, and a third level for a third set of buckets designated as “base”. The techniques include receiving delta updates of space accounting (SA) statistics at buckets of the active set, in which the SA statistics are associated with IDs from a large sparse ID space. The techniques include, once the buckets of the active set are full, switching the “active” and “de-staging” designations of the first and second sets of buckets, respectively, and de-staging and merging, bucket-by-bucket, the SA delta updates contained in the de-staging set with any SA delta updates contained in the base set.

Systems and methods of updating sparse metadata in metadata delta log (MDL)-based storage clusters

Techniques for processing a read I/O operation that reads first content stored at a target logical address can include: determining, using the target logical address as a first key to index into a first cache, whether the first cache includes a first cache entry caching first metadata used to access a first physical storage location including the first content stored at the target logical address; responsive to determining the first cache includes the first cache entry, determining, using the first metadata as a second key to index into a second cache, whether the second cache includes a second cache entry caching the first content stored at the target logical address; and responsive to determining the second cache includes the second entry, returning the first content from the second entry of the second cache in response to the read I/O operation.

Caching techniques using a two-level read cache

A technique for managing metadata changes in a storage system provides different aggregation policies for use with different metadata. The technique includes assigning metadata changes to respective aggregation policies and storing the assigned metadata changes in a set of data structures. The technique further includes destaging the metadata changes from the set of data structures separately for the different aggregation policies in accordance with settings specific to those aggregation policies.

Processing metadata changes using multiple aggregation policies

Nodes in a storage system can autonomously ingest I/O requests and flush data to storage. First and second nodes determine a sequence separator, the sequence separator corresponding to an entry in a page descriptor ring that separates two flushing work sets (FWS). The first node receives an input/output (I/O) request and allocates a sequence identification (ID) number to the I/O request. The first node determines a FWS for the I/O request based on the sequence separator and the sequence ID number, and commits the I/O request using the sequence ID number. The I/O request and the sequence ID number are sent to the second node.

Autonomous I/O ingestion and data flushing among nodes in storage systems

Data replication techniques can include receiving, at a source system, a write directed to a source logical device configured for asynchronous remote replication to a destination system; performing processing that flushes a transaction log entry for the write; and performing replication processing that uses a replication queue including a replication queue entry corresponding to the write that stores the first content to a logical address. The processing can create a metadata (MD) log entry in a MD log for the write responsive to determining that the write is directed to the source logical device configured for asynchronous remote replication and that the first content has not been replicated. Responsive to the first content not being in cache, the first content can be retrieved using the reference to a storage location storing the first content. The reference can be obtained from the MID log entry or the replication queue entry.

Replication techniques using a metadata log

In at least one embodiment, processing can include: receiving, at a first node, a read operation that reads content of a logical address, wherein a second node, but not the first node, owns the logical address; and performing optimized read processing for the read operation. The optimized read processing can include: performing, in parallel, first processing that obtains a first address hint and first content corresponding to the logical address, and second processing that obtains a second address hint corresponding to the logical address; determining whether the first and second address hints match; if the first and second address hints match, determining that first content is valid content stored at the target logical address; if the first and second address hints do not match, determining the first content is not stored at the logical address, and using the second address hint to obtain second content stored at the logical address.

Double-mapping technique of I/O latency optimization

Techniques for providing a virtual federation approach to increasing efficiency of processing circuitry utilization in storage nodes with a high number of cores. The techniques include, for each of two (2) physical nodes, logically partitioning a plurality of cores into a first domain of cores and a second domain of cores. The techniques include designating the first domain of cores of each physical node as belonging to a first virtual node. The techniques include designating the second domain of cores of each physical node as belonging to a second virtual node. The techniques include operating the first virtual nodes on the two (2) underlying physical nodes as a first virtual appliance, and operating the second virtual nodes on the two (2) underlying physical nodes as a second virtual appliance. In this way, scalability and speedup efficiency can be increased in a multi-core processing environment with a high number of cores.

Virtual federation approach for efficient CPU utilization in storage systems with high number of cores

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Pardes-Hana, Israel

Vladimir Shveidel