Emc Corporation

Rui Liang

Sorin Faibish

Xiaoye Jiang

Paul M Bober

Jeffrey Louis Alexander

Stephen A Fridella

Jiannan Zheng

Mark K Ku

Gang Ma

A storage object such as a virtual disk drive or a raw logical volume is contained in a UNIX compatible file so that the file containing the storage object can be exported using the NFS or CIFS protocol and shared among UNIX and MS Windows clients or servers. The storage object can be replicated and backed up using conventional file replication and backup facilities without disruption of client access to the storage object. For client access to data of the storage object, a software driver accesses the file containing the storage object. For example, a software driver called a virtual SCSI termination is used to access a file containing a virtual SCSI disk drive. Standard storage services use the SCSI over IP protocol to access the virtual SCSI termination. An IP replication or snapshot copy facility may access the file containing the virtual SCSI disk drive using a higher-level protocol.

Multi-protocol sharable virtual storage objects

To permit multiple unsynchronized processors to update the file-modification time attribute of a file during concurrent asynchronous writes to the file, a primary processor having a clock manages access to metadata of the file. A number of secondary processors service client request for access to the file. Each secondary processor has a timer. When the primary processor grants a range lock upon the file to a secondary, it returns its clock time (m). Upon receipt, the secondary starts a local timer (t). When the secondary modifies the file data, it determines a file-modification time that is a function of the clock time and the timer interval, such as a sum (m+t). When the secondary receives an updated file-modification time (mp) from the primary, if mp&#x3e;m+t, then the secondary updates the clock time (m) to (mp) and resets its local timer.

Management of the file-modification time attribute in a multi-processor file server system

Mechanisms and techniques disclose a system that provides access to data using a two part cache. The system receives a data access request containing a first data reference, such as an open systems request to access data. The system then obtains a history cache entry from a history cache based on the first data reference and obtains a partition cache entry from a partition cache based on the first data reference. Cache entries contain mappings between open systems reference locations and non-open systems references to locations in the data to be accessed. The system then performs a data access operation as specified by the data access request using a second data reference based upon either the history cache entry or the partition cache entry. Upon performance of the data access operation, the system then updates the history and partition caches with new cache entries and can resize the partition and history caches as needed.

Methods and apparatus for accessing data using a cache

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Natick, MA, United States of America

Rui Liang