Microsoft Technology Licensing, LLC

Alexander Budovski

Cristian Diaconu

Naveen Prakash

Alejandro Hernandez Saenz

Krystyna Ewa Reisteter

Huanhui Hu

Hanumantha Rao Kodavalla

Sandeep Lingam

Peter Byrne

Rogerio Ramos

Rogério Ramos

Sheetal Shrotri

Eric Dean Lee

Ashmita Raju

Srikanth Sampath

Distributed database systems including compute nodes and page servers are described herein that enable separating logical and physical storage of database files in a distributed database system. A distributed database system includes a page server and a compute node, and is configured to store a logical database file that includes data and is associated with a file identifier. Each page server is configurable to store slices (i.e., subportions) of the logical database file. The compute node is coupled to the plurality of page servers and configured to store the logical database file responsive to a received command. In an aspect, such storage may comprise slicing the data comprising the logical database file into a set of slices with each being associated with a respective page server, maintaining an endpoint mapping for each slice of the first set of slices, and transmitting each slice to the associated for storage thereby.

Separation of logical and physical storage in a distributed database system

Distributed database systems including compute nodes and page servers are described herein that enable separating logical and physical storage of database files in a distributed database system. A distributed database system includes a page server and a compute node and is configured to store a logical database file that includes data and is associated with a file identifier. Each page server is configurable to store slices (i.e., subportions) of the logical database file. The compute node is coupled to the plurality of page servers and configured to store the logical database file responsive to a received command. In an aspect, such storage may comprise slicing the data comprising the logical database file into a set of slices with each being associated with a respective page server, maintaining an endpoint mapping for each slice of the first set of slices, and transmitting each slice to the associated for storage thereby.

Methods, systems and computer program products are provided for transaction log validation in a database transaction log service. A transaction log service may perform egress validation to confirm transaction logs match previously served transaction logs and are free of corruption. A transaction log service may determine whether a transaction log (e.g., in the form of a log block) was previously served based on transaction log (e.g., log block) identity indicating a position in a logical stream of transaction logs (e.g., log blocks). Egress validation may improve log service reliability by providing an added layer of defense against corruption of a transaction log payload.

Transaction log validation in a database transaction log service

Methods, systems, and computer program products are provided for consolidating transaction log requests and transaction logs in a database transaction log service. A scalable log service may manage log requests and logs to reduce resource consumption, such as memory and I/O. Log requests may be managed by consolidating (e.g., organizing, merging and/or de-duplicating) the log requests. Transaction log requests may be mapped to read requests for transaction log storage devices in less than a one-to-one ratio. Transaction logs may be managed by using the consolidated log requests to consolidate (e.g., and prefetch) transaction logs from multiple cache and/or storage tiers to a log pool cache. Log requests may be served from the log pool cache.

Consolidating transaction log requests and transaction logs in a database transaction log service

Embodiments described herein detect data corruption in a distributed data set system. For example, a system comprises node(s) for processing queries with respect to a distributed data set comprising a plurality of storage segments. A write transaction resulting from a query with respect to a particular storage segment is logged in a log record that describes a modification to the storage segment. A log service provides the log record to a data server managing a portion of the distributed data set in which the storage segment is included, which performs the write transaction with respect to the storage segment. For redundancy purposes, the data server has replica(s) that manage respective replicas of the portion of the distributed data set managed thereby. For backup purposes, snapshots of the replica(s) are periodically generated. To determine a data corruption, a snapshot of one replica is cross-validated with a snapshot of another replica.

Snapshot-based data corruption detection

Brokering log records so as to prevent log records that are not yet persisted in a persistent log from being disseminated. The log records may be generated as a primary compute system performs operations. Upon receiving a request for a log record, the broker component determines whether the requested log record has been persisted in a persistent log. If the broker component determines that the log record has been persisted in the persistent log, the broker component responds to the request by causing the requested log record to be provided to the requesting entity (e.g., a secondary compute system). On the other hand, if the log record cannot yet determine that the log record has been persisted in the persistent log, the broker component prevents the log record from being provided to the requesting entity. This prevents data from being inconsistent during recovery.

Brokering persisted and unpersisted log records

The bifurcation of a log into a fixed-size log portion and a growable log portion. Log records are first written to the fixed-size log portion. At some point, the older log records within the fixed-size log portion are destaged to the growable log portion. Destaging may involve copying the log records from the fixed-size log portion and tacking the log record onto the end of the growable log portion. This destaging might occur one sub-portion (e.g., one virtual log file) at a time. The more recent log records are within the fixed-size log portion. Accordingly, new writes to the log occur to the fixed-size log portion. Furthermore, a large portion of the reads are of the more recent log records within the fixed-size log portion. Thus, optimizing performance within the fixed-size log portion results in significant improvement in the performance of the overall log.

Log destaging from fixed-size log portion

The use of log marking (otherwise known as 'coloring') of sub-portions of a log that records actions (e.g., data operations) performed by a computing system. The log is composed of multiple sub-portions, such as virtual log files, which are successively added to the log as the log grows. For instance, the sub-portions may be virtual log files of the log. The principles described herein change the use of log marking depending on which sub-portion of the log is being marked. If the computing system fails, and recovery is needed, the recovery process can thus deterministically identify where the last written log record is.

Log marking dependent on log sub-portion

Use of a log service computing system to apply a log to storage segments in the context of there being a primary compute system that operates upon data, and secondary compute system(s) that are at the ready to be promoted to the new primary compute system should the old primary compute system fail. Rather than have each of the primary and secondary compute systems maintain their own replicated of the entire data locally, the data is separated in storage segments that are collectively distributed amongst multiple storage segment servers.

Applying a log to storage segments

The mounting a drive to two or more computing systems. For instance, the drive may be mounted to a first computing system so as to be writable (and potentially readable) by the first computing system. But also, the drive is also mounted to one or more other computing systems so as to be only readable by those one or more computing systems. This allows for multiple computing systems to have access to the drive without risk that the data thereon will become corrupt. In one embodiment, the only user data stored on that drive is a single file of fixed size. Thus, even when user data is written into the fixed-size file, the management data stored (that keeps track of the files) on the drive does not change.

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Snohomish, WA, United States of America

Alexander Budovski