Uresh K Vahalia

6389420, May 14, 2002

Sep 30, 1999

09/410514

Uresh K. Vahalia - Waban MA
Xiaoye Jiang - Shrewsbury MA
Jeffrey Jon Darcy - Lexington MA
Boris Zuckerman - Marblehead MA
Ronald Curtis Searls - North Andover MA

EMC Corporation - Hopkinton MA

G06F 1730

707 8, 707 10, 707201, 709248

File locks and file metadata are distributed from a file manager to clients in a data network to permit the clients to share access to file data in data storage. The file manager is permitted to grant a second lock upon the file data without necessarily receiving notification from a client that it has relinquished a first lock on the file data while ensuring that conflicting locks are never granted. The client sets the beginning of a first period of time over which the client may access the file data once the first lock on the file data has been granted by the file manager, and the client sends a lock request to the file manager. The file manager responds by setting the beginning of a second period of time such that the first period of time is certain to have expired once the second period of time has expired, granting the first lock upon the file data to the client, and transmitting a lock grant message to the client. The client receives the lock grant message, and accesses the file data so long as the clients access to the file data will be completed by expiration of the first period of time.

6453354, Sep 17, 2002

Mar 3, 1999

09/261626

Xiaoye Jiang - Shrewsbury MA
Uresh K. Vahalia - Waban MA
Uday Gupta - Westford MA
Percy Tzelnic - Concord MA

EMC Corporation - Hopkinton MA

C06F 1516

709229, 709213

A first data mover computer services data access requests from a network client, and a second data mover computer is coupled to the first data mover computer for servicing data access requests from the first data mover computer. The first data mover computer uses a connection-oriented protocol to obtain client context information and to respond to a session setup request from the client by authenticating the client. Then the first data mover computer responds to a file system connection request from the client by forwarding the client context information and the file system connection request to the second data mover computer. Then the first data mover computer maintains a connection between the first data mover computer and the second data mover computer when the client accesses the file system and the first data mover computer passes file access requests from the client to the second data mover computer and returns responses to the file access requests from the second data mover computer to the client. In a preferred embodiment, the connection-oriented protocol is the Common Internet File System (CIFS) Protocol, and multiple clients share a Transmission Control Protocol (TCP) connection between the first data mover computer and the second data mover computer by allocation of virtual channels within the shared TCP connection and multiplexing of data packets of the virtual channels over the shared TCP connection.

6571259, May 27, 2003

Sep 26, 2000

09/669347

Jiannan Zheng - Framingham MA
Xiaoye Jiang - Shrewsbury MA
Uresh Vahalia - Waban MA

EMC Corporation - Hopkinton MA

G06F 1200

707205, 707202, 707206, 710 74

A file server provides transaction processing capabilities previously supplied by the operating system of a host computer. On-disk file system metadata is changed only at commit time, and a transaction log protects the transition. The disk state can only be a consistent state, resulting from a commit operation. All disk-block reservation and pre-allocation mapping are in the memory, and after a crash, they are automatically discarded. The file server therefore relieves the client of processing burden and also reduces network traffic. In addition, the file server can more efficiently perform the transaction processing capabilities and reduce the frequency of access to storage by judicious allocation of file system blocks and transfer of file system blocks between file system objects, cache memory, and the transaction log. The differentiation between preallocation states and allocation states of in-memory file system blocks also permits application programs to more efficiently transfer data between files.

6625591, Sep 23, 2003

Sep 29, 2000

09/675485

Uresh Vahalia - Waban MA
Sudhir Srinivasan - Chalmsford MA

EMC Corporation - Hopkinton MA

G06F 1730

707 1, 707 3, 707 10, 711216, 711221

To accelerate searching of large file system directories, hashing information for a selected directory is compiled and retained in random access memory prior to a need for access to the directory to satisfy a file access request from an application. No change in the on-disk file system representation is required, nor is there any need for nonvolatile storage of the hashing information. If memory is scarce, the hashing information can be incomplete yet give hints for searching the most-recently-accessed directory entries. In a preferred implementation, the hashing information for a directory includes a hash table for searching for names of objects such as files, subdirectories or links in the directory, and a hash table for searching for free space in the directory.

6625750, Sep 23, 2003

Nov 16, 1999

09/440756

Wayne W. Duso - Shrewsbury MA
Leslie E. Kuczynski - Belmont MA
John Forecast - Newton MA
Uday Gupta - Westford MA
Uresh K Vahalia - Newton MA
Dennis P. J. Ting - Groton MA

EMC Corporation - Hopkinton MA

H02H 305

714 11, 714 4, 714 13

A file server includes a plurality of stream server computers linking data storage to a data network, and at least two controller servers for controlling the stream server computers. The controller servers are programmed so that at a given time one of the controller servers is active in controlling the stream server computers, and another of the controller servers is inactive. The inactive controller server is programmed to respond automatically to a failure of the active controller server by becoming active. For example, each of the controller servers has a respective flag for indicating whether or not the controller server is active. Each controller server is programmed so that, upon booting, it will read the flag of the other stream server, and if the flag of the other controller server indicates that the other controller server is active, then the controller server becomes inactive. Otherwise, the stream server assumes an active or inactive state based on a predetermined arbitration method. The active controller server also reports failure conditions to a customer service center, monitors the inactive controller server to ensure that the inactive controller server is in a state of readiness, and monitors itself to determine whether it should become inactive.

6714952, Mar 30, 2004

Nov 10, 1999

09/438137

Scott Dunham - Billerica MA
Rulian Fiske - Wayland MA
Hal Hansen - Tewksbury MA
Sanjay Jain - Shrewsbury MA
Madhav Mutalik - Southboro MA
Edgar St. Pierre - Fall River MA
Puneet Lal - Shrewsbury MA
Uresh Vahalia - Waban MA

EMC Corporation - Hopkinton MA

G06F 1200

707204, 707 10, 711161, 711162

Described is a technique for a backup and restoration of data in a network that includes a multi-lingual file system and a multi-lingual network file server. Multiple meta data files are associated with a single data file in the network. Provided are services for packaging the metadata as a single parameter of an application programming interface (API) for a particular data file being backed up or restored over a network. These techniques may be used in both full and incremental backups and restores of data over a network.

6816891, Nov 9, 2004

Sep 26, 2000

09/670454

Uresh K. Vahalia - Waban MA
Uday Gupta - Westford MA
Betti Porat - Newtonville MA
Percy Tzelnic - Concord MA

EMC Corporation - Hopkinton MA

G06F 15167

709214, 709225, 711118

A network file server includes a first set of data processors for receiving requests from clients, and a second set of data processors for accessing read-write file systems. A respective data processor in the second set is assigned to each file system for exclusive management of read and write locks on the file system. Each data processor in the first set can authorize access to file systems directly accessed by more than one data processor in the second set. Processing of a request for access that is assigned to manage the locks on the file system to be accessed. The exclusivity of lock management eliminates cache coherency problems, and dynamic load balancing can be used to prevent the lock management from becoming a bottleneck to performance.

6823336, Nov 23, 2004

Sep 26, 2000

09/669939

Sudhir Srinivasan - Chelmsford MA
Uresh Vahalia - Waban MA
Uday K. Gupta - Westford MA
Philippe Armangau - Acton MA

EMC Corporation - Hopkinton MA

G06F 1730

707 8, 707201

A data storage system receives sets of the revisions such that each set of revisions changes the dataset from one consistent state to another. Each set of revisions is processed in a write-selected phase followed by a read-selected phase. In the write-selected phase, the revisions in each set are written to a buffer and processed to produce a directory of the set of revisions. In the read-selected phase, the revisions are read from the buffer and integrated into the dataset. When one set of revisions is in the read-selected phase, the next set of revisions is in the write-selected phase. To permit uninterrupted read-only access to a consistent state of the dataset, the data storage system responds to a request for reading specified data on a priority basis by first accessing the directory of the read-selected revisions to determine whether the specified data are in the read-selected set of revisions, and if so, the specified data are read from the read-selected set of revisions, and if not, the specified data are read from the dataset. In a preferred implementation, the sets of revisions are alternately written to either a first buffer or a second buffer, and processing of each set of revisions is switched from the write-selected phase to the read-selected phase by switching between the two buffers.