Ncr Corporation

Lawrence J Schroeder

Robert W Fish

Jin Wang

Dennis B Beasley

A method for detecting communication failures on a network comprising a server computer connected to multiple client computers, said server and client computers communicating through the transmission of data packets via the network. The method includes the step of periodically sending an echo request message from the server computer to the client computers. Each client computer, following receipt of the echo request message, sends an echo reply message back to the server computer. The method further includes the steps of monitoring the rate at which data packets are received by the server computer; and reducing the frequency at which echo request messages are sent from the server computer to the client computers during periods when the rate at which data packets are received by the server computer exceeds a re-configurable rate value. The frequency at which the echo request messages are sent is dependent upon the rate at which data packets are received by said server computer.

Low overhead method for detecting communication failures on a network

An improved file system for managing data storage and retrieval in a clustered UNIX computer system including a plurality of processing nodes and an interconnection network connecting the processing nodes. The improved file system includes a data storage device, such as a disk storage unit, connected via a shared SCSI interconnect with each one of the processing nodes, rather than connected directly with a single processing node. The structure layout for the file system, which is maintained on the data storage device, includes sufficient information to enable all of the processing nodes to access said file system. The layout comprises: superblocks containing offsets to all other file system structures within the file system; a free inode bit map containing a plurality of bits, each bit representing an inode within the file system; a modified inode journal containing a separate inode bit map for each superblock and identifying particular inodes which have been modified by the file system prior to a system failure; a plurality of inodes, each inode being a data structure which contains a definition for each particular file and directory in the file system; a free block bit map containing a bit map wherein each distinct bit represents a logical disk block in the file system; and data blocks containing data representing file contents. The file system interfaces with the computer system's distributed lock manager (DLM) to coordinate file system usage.

File system for a clustered processing system

A method for identifying and repairing file system damage following the failure of a processing node within a clustered UNIX file system including a plurality of processing nodes, an interconnection network connecting the processing nodes, and a data storage device connected via a shared interconnect with each one of the plurality of processing nodes. The method includes the step of maintaining a journal for each processing node, each journal containing a bit map identifying inodes to which its associated processing node has acquired and retains an exclusive right. Each bit map journal is updated whenever its associated processing node acquires an exclusive right to an inode. Following a failure of a processing node, a non-failed processing node is designated to audit the inodes associated with the failed node. Auditing is accomplished by reading the bit map journal associated with the failed processing node and obtaining the exclusive right to every inode found within the journal. The inodes within the bit map journal, referred to as suspect inodes, are then compared with a global bit map which identifies each and every unit of space within the file system that is assignable. A suspect node is identified as having a transient state when the unit of space assigned to the suspect inode is also found to be assignable. The assignment of a unit of file system space to any suspect inode identified as having a transient state is thereafter discarded.

Growing community of inventors

Wheaton, IL, United States of America

Lawrence J Schroeder