International Business Machines Corporation

Owen Theodore Anderson

Frank Bernhard Schmuck

Craig Fulmer Everhart

Boaz Shmueli

Felipe Knop

Deepavali M Bhagwat

Enci Zhong

Hai Zhong Zhou

Binny Sher Gill

D Scott Guthridge

Geoffrey Albert Riegel

Manuel Vasconcellos Pereira, Iii

Wayne A Sawdon

Abhishek Jain

John Lewars

Subashini Balachandran

Kuei-Yu Wang-Knop

Leo Shyh-Wei Luan

Leo S Luan

Huzefa Pancha

Mansi Ajit Shah

Shashank Gugnani

Snapshot restoration based on a correlation of a snapshot namespace with a file system namespace is provided. A restore command is received, following which the correlation between the file system namespace of the file system with the snapshot namespace of a snapshot of the file system is performed. Further a file operation command is received to perform at least one of a read file operation and a lookup file operation, corresponding to at least one object associated with the file system namespace of the file system. Further, based on restoration data associated with the at least one object, a redirection operation is executed for at least one of the read file operation and the lookup file operation. The redirection operation routes the file operation command to at least one respective snapshot object associated with the snapshot namespace, corresponding to the at least one object.

Instant file system snapshot restoration

Provided are a computer program product, integrated cache manager, and method for maintaining data in a first level memory and buckets representing regions of memory devices to extend data cache. A plurality of buckets represent distinct regions of memory devices. The buckets are associated with different threshold access count ranges. Data having an access count is stored in one of the buckets associated with a threshold access count range including the access count of the data to store. Data evicted from a first level memory is copied to an initial bucket comprising one of the buckets. Data is moved from a source bucket comprising one of the buckets, including the initial bucket, to a target bucket of the buckets having a target threshold access count range including an access count of the data to move.

Maintaining data in a first level memory and buckets representing regions of memory devices to extend data cache

Provided are a computer program product, system, and method for switching serialization techniques for handling concurrent write requests to a shared file. A first node serializes write requests from client nodes to write to the shared file. The first node determines whether to switch to a second node to manage write quests to the shared file based on a pattern of write requests to the shared file. The client nodes are notified to direct write requests to the shared file to the second node in response to determining to switch to the second node. The second node processes write requests to the shared file to serialize writes to the shared file after the client nodes are notified to submit the write requests to the shared file to the second node.

Switching serialization techniques for handling concurrent write requests to a shared file

A method for executing operation requests includes formatting one or more storage devices and selecting one or more labeled replicas and one or more distinguished replicas, receiving an operation request with respect to a set of data blocks, identifying a preferred replica corresponding to the received operation request, determining whether the replication-pending bits for the preferred replica are set, and executing the received operation request with respect to the corresponding distinguished replica. A method for executing a write operation request additionally includes setting replication-pending bits with respect to the labeled replica, wherein the replication-pending bits indicate an incomplete write request, writing data to both a labeled replica and a distinguished replica, and clearing the replication-pending bits with respect to the labeled replica to indicate the completion of the write operation. A method for executing a read operation additionally includes identifying a preferred replica with respect to the received read request.

Interrupted replicated write recognition

A method and a computer system for asymmetric replication of data are provided. Storage of a set of data is organized as a first copy and as a second copy in non-volatile storage. The second copy is reliable and stored so as to be readable at a speed slower than for the first copy. A read instruction regarding the set of data is received and performed preferentially via the first copy such that the asymmetric replication achieves enhanced performance speed. A request to execute a write operation is received. The write operation is executed to the first copy and to the second copy. In response to determining that the write operation to the first copy was unsuccessful, a label for the first copy is set as stale.

Efficient use of optional fast replicas via asymmetric replication

A computer-implemented method includes using a cache replacement algorithm to forcefully evict target data from a cache. Using the cache replacement algorithm includes selectively accessing data in the cache. A computer program product includes one or more computer readable storage media and program instructions collectively stored on the one or more computer readable storage media. The program instructions include program instructions to perform the foregoing method. A system includes a processor and logic integrated with the processor, executable by the processor, or integrated with and executable by the processor. The logic is configured to perform the foregoing method.

Fine-grained forced cache eviction

A computer-implemented method enables efficient tracking of fileset IDs and inode utilizing a fileset mask and an internal inode mask. A utility dynamically updates the fileset mask and the internal inode mask to enable mapping of the number of one (1) bits in the fileset mask to a fileset identifier (ID) and mapping of the one bits in the inode mask to an inode number for the fileset, as either the number of filesets or the number of inodes required per filesets increases above a next power of two threshold. The one bits within the fileset mask and the internal inode mask are disjoint relative to each other. An external inode number is mapped to a corresponding fileset and to a corresponding inode number by concatenating individual bits of the external inode number corresponding to each one (1) bit within the fileset mask and the inode mask.

Fileset masks to cluster inodes for efficient fileset management

A system and method is disclosed for maintaining, in a Storage Area Network (SAN), the consistency of a local copy of a remote file system sub-tree obtained from a remote source. Directory structure of the remote file system sub-tree is mapped to a remote container attached to the SAN and each remote object of the remote file system sub-tree is represented as a local object component of the remote container. Next, each of the local objects are labeled with attributes associated with the represented remote object, and metadata describing each of the local objects is stored in a metadata server. Also, a consistency policy is associated with each of the local objects in the remote container (wherein the policy defines conditions for checking freshness of said labeled attributes), and the local object components of remote container is updated in accordance with the consistency policy.

Remote access agent for caching in a SAN file system

A method for avoiding directory conflicts across a file system having multiple nodes with one node representing a token manager. For each directory, at least one metanode responsible for directory updates. The method involving obtaining a name-based lock on a filename. Querying the token manager for a lock token. If a new token is obtained, sending a Remote Procedure Call (RPC) to the metanode to obtain matching directory entries, and caching the result of the RPC so that subsequent operations on that filename can be satisfied without additional messages sent to the metanode. Updating a cached directory block in memory by creating a new directory entry in the block or deleting an existing directory entry from the block. Information regarding the updating is sent to the metanode on one of: periodic schedule, a subsequent synchronization event, or when the name-based lock token is revoked.

Concurrent directory update in a cluster file system

Improved techniques are disclosed for accessing content in file systems, allowing file system clients to realize advantages of file system referrals even though a file access protocol used by the client is not specifically adapted for referral objects. (For example, the client may have a legacy file system protocol or a proprietary file system protocol which does not support referrals.) These advantages include a uniform name space view of content in a network file system, and an ability to locate content in a (nearly) seamless and transparent manner, even though the content may be dynamically moved from one location to another or replicated in different locations. A file system server returns a symbolic link in place of a referral, and an automated file mounting process on the client is leveraged to access the content using the link. Built-in crash recovery techniques of the file system client are leveraged to access moved content.

Uniform name space referrals with location independence

Addressed is a system and method for remote data caching and replication by local copy maintenance of remote data within a SAN file system. Distributed Storage Tank (DST), an extension to a SAN file system, provides for transparent SAN client access of local copies by importing, exporting, and storing data using network file access protocols as well as by providing assurance of metadata and file content validity. A Remote Access Agent (RAA) handles protocol implementation and conversion necessary for communication with remote data sources. Controlled by a consistency policy, consistency is maintained by RAA fetching and updating local copies if modifications have occurred to a file since it was first stored as a local copy in local storage. Additionally, RAA returns metadata pertaining to the requested data. A SAN client obtains metadata corresponding to the requested data and utilizes it to directly access locally stored copies of remote data.

A system provides referencing from one file system server to another through the use of a file system location database, improving movement and replication of file systems. When a file system is moved from a first file system server, a data object that references the file system remains in the first server and contains information used to find the current location of the file system. The actual location of the file system is stored in the separate file system location database, which contains the locations of file systems on a number of file system servers. This allows the data in a file system to be replicated or moved without requiring updates to the data in any redirecting or referencing servers.

Method, apparatus, and program for separate representations of file system locations from referring file systems

In one form, in a method for making file systems accessible, a referring file system attribute is created, responsive to a first file system having a referral object referring to a second file system. The referring file system attribute describes referring file system identification for the first file system. A path attribute is created, responsive to the first file system having the referral object, describing a path from a root of the first file system to the referral object. A referred file system attribute is created, responsive to the first file system having the referral object, describing a referred file system identification for the second file system. A parent attribute is created, responsive to the first file system having the referral object, describing a parent flag for the second file system.

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Chapel Hill, NC, United States of America

Owen Theodore Anderson