Emc IP Holding Company LLC

Suraj Raju

Max Laier

Ronald Steinke

Ron Steinke

Douglas Kilpatrick

Jonathan Mark Walton

Antony Richards

Cornelis Van Rij

Jefferey Roberson

Travis Lane

Systems and methods for mirroring a file system journal are described herein. A method as described herein can include receiving, by a system operatively coupled to a processor, transactional file system updates corresponding to a write operation to be performed at a first node of the system; transferring, by the system, the transactional file system updates from an initiator node of the system to a first journal at the first node and a second journal at a second node of the system that is logically distinct from the first node and the initiator node; and committing, by the system, the transactional file system updates to the first journal and the second journal.

System and method for mirroring a file system journal

Direct read in clustered file systems is described herein. A method as described herein can include determining, for a write operation on a resource stored by a data storage system, as initiated by an initiator node, a reference count for the resource, the reference count comprising a number of target storage regions of the data storage system to be modified by write data during the write operation; facilitating conveying, from the initiator node to a lock coordinator node, the reference count for the resource; facilitating conveying, from the initiator node to respective participant nodes that are respectively assigned to the target storage regions, the write data and a key value for the write operation; and facilitating causing the respective participant nodes to convey respective notifications that comprise the key value in response to the respective participant nodes writing the write data to the target storage regions.

Direct read in clustered file systems

Incremental inline journaling in a journaled file system can be utilized to facilitate concurrency and throughput of a journaled file system. In an example, a request can be received for a transaction to modify a sub-block portion of a file stored in a distributed storage system. In response to that, the modification can be allocated to a data structure in a journal of the distributed storage system. After the transaction commits, a current value of the sub-block portion of the file can be saved to the delta structure. Then, a new value corresponding to the request for the transaction to modify the sub-block portion of the file can be written to the metadata block. After writing the new value to the metadata block, a memory space used to store the delta structure can be freed.

Incremental inline journaling in a journaled file system

A self-optimizing interval detection data structure is provided herein. A data storage system as described herein can include a memory that stores computer executable components and a processor that executes computer executable components stored in the memory. The computer executable components can include a candidate assignment component that maps properties of a resource of the data storage system to respective candidate data structures; a latency estimation component that estimates respective latencies associated with the respective candidate data structures; and a selection component that selects a candidate data structure of the respective candidate data structures having a latency that is less than a threshold latency, resulting in a selected data structure.

Self-optimizing interval detection data structure

Checking data integrity in incremental journaling

Harmonization of failure domains in a distributed system is provided herein. A data storage system as described herein can include a memory that stores computer executable components and a processor that executes computer executable components stored in the memory. The computer executable components can include a node assignment component that assigns computing nodes in the data storage system to respective failure domains of a set of data failure domains, a hashing component that generates hashing information associated with respective computing nodes of the computing nodes assigned to a selected failure domain of the set of failure domains, and a group update component that designates at least one computing node of the computing nodes in the selected data failure domain to perform an operation associated with the hashing information.

Harmonization of failure domains in a distributed system

Extended group service changes are facilitated in a data storage system. Node devices of a data storage system are identified that are merging into a cluster of the node devices. In response to the identifying, respective merge locks are caused at a group of the node devices that are sending service updates.

Extended group service changes

Implementations are provided herein for using a Node State Block ('NSB') to track the validity of various copies of the journal. The NSB can contain states local to the node and be implemented independent of the cluster state, and be readable at node boot time. The NSB can be mirrored to every storage drive within the node. The NSB can contain a generation number and a validity bit. Every time the NSB is updated, the generation number can be incremented. An update must be written to a quorum of drives to be considered committed. At mount time, the NSB is read from all the drives, and the copy with the highest generation number is used. If a quorum of drives cannot be read, the mount fails. Read quorum, or the quorum required at mount when reading the NSB across the set of storage drives requires a strict majority of the storage drives to have valid copies of the NSB. Write quorum, or the quorum required to update the NSB across all storage drives, requires a simple majority of drives.

Mirrored block with quorum set management for use in tracking valid mirrors of a journal

Implementations are provided herein for a node among a cluster of nodes to maintain copies of its journal both locally and on a buddy node. Each copy of the journal can be associated with a validity bit and a clean bit that can be provided as inputs to a journal mirror state machine that can be used to maintain consistency between local copies of the journal and mirrored copies of the journal. The node can operate in a read-only mode or a read-write mode, whereby operating in read-only mode prevents changes to the local journal. The status of the mirror copy of the journal can be established in a link status depending on its availability. The journal can then transition between various states of the state machine upon triggering events that change the link status or the mode of the node. It can be appreciated that the transitioning among states of the state machine can provide crash-consistency for the filesystem during operation.

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Issaquah, WA, United States of America

Suraj Raju