Emc Corporation

Aju John

Uday K Gupta

Uresh K Vahalia

Philippe Armangau

Percy Tzelnic

Frederic Corniquet

John Michael Hayden

Dennis P J Ting

Paul M Bober

Jeffrey Louis Alexander

Hongmei Wang

Pascal Donette

For disaster recovery of a file server at an active site, the files that define the user environment of the file server are replicated to a virtual server at a disaster recovery site. To switch over user access from the active site to the disaster recovery site, the disaster recovery system determines whether there are sufficient network interfaces and file system mounts at the disaster recovery site. If so, the required resources are reserved, and user access is switched over. If not, an operator is given a list of missing resources or discrepancies, and a choice of termination or forced failover. Interruptions during the failover can be avoided by maintaining a copy of user mappings and a copy of session information at the disaster recovery site, and keeping alive client-server connections and re-directing client requests from the active site to the disaster recovery site.

Internet protocol based disaster recovery of a server

A file system is migrated from a source file server to a target file server in a data network while permitting clients to have concurrent read/write access to the file system. The target file server issues directory read requests and file read requests to the source file server in accordance with a network file access protocol to transfer the file system from the source file server to the target file server. Concurrent with the transfer of the file system from the source file server to the target file server, the target file server responds to client read/write requests for access to the file system. In a preferred embodiment, the target file server maintains a hierarchy of on-line nodes off-line nodes. The online nodes represent file system objects that have been completely migrated, and the offline nodes representing file system objects that have not been completely migrated. The target file server executes a background process that walks through the hierarchy in order to migrate the objects of the offline nodes. When an object has been completely migrated, the target file server changes the offline node for the object to an online node for the object.

Concurrent file across at a target file server during migration of file systems between file servers using a network file system access protocol

There is a performance loss associated with servicing a pipe or stream for a connection oriented process by maintaining a connection between a server thread and a client for a series of messages. As a result of maintaining this connection, there is less balance; some threads work harder than others, causing a loss of performance. To solve this problem, a collector queue combines messages from the connection oriented process with messages from the other concurrent processes. The threads receive messages from the collector queue rather than individual pipes. Any idle thread can pick up a message from the collector queue. The collector queue keeps track of which pipe each message came from so that the reply of the server to each message is directed to the same pipe from which the message came from. Therefore the collector queue ensures thread balance and efficiency in servicing the messages. In the preferred implementation, each entry in the collector queue includes a message pointer and a pipe pointer. The message pointer points to allocated memory storing the message in a message buffer. The pipe pointer points to the pipe from which the message originated. The collector queue is a singly linked list. A free thread takes an entry off the collector queue, interprets the message of the entry, sends a reply, and deallocates the memory of the entry and the allocated memory storing the message in the message buffer.

Network file server having a message collector queue for connection and connectionless oriented protocols

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Northborough, MA, United States of America

Aju John