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Protocol for Atomic Striped File Access in a Striped File System

IP.com Disclosure Number: IPCOM000114161D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 260K

Publishing Venue

IBM

Related People

Baylor, SJ: AUTHOR [+3]

Abstract

Disclosed are two protocols designed to guarantee atomic execution of read and write access requests that span multiple file server nodes in a parallel file system. Both protocols require communication only among the file server nodes, and require a number of messages at most equal to the number of file server nodes. The first protocol requires the receipt of a single message from the requesting site at each file server node that possesses accessed data. With some restrictions on the distribution of file data to the file server nodes, a modification of the protocol can execute completely with the receipt of a message from the requesting site at only one file server node.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 22% of the total text.

Protocol for Atomic Striped File Access in a Striped File System

      Disclosed are two protocols designed to guarantee atomic
execution of read and write access requests that span multiple file
server nodes in a parallel file system.  Both protocols require
communication only among the file server nodes, and require a number
of messages at most equal to the number of file server nodes.  The
first protocol requires the receipt of a single message from the
requesting site at each file server node that possesses accessed
data.  With some restrictions on the distribution of file data to the
file server nodes, a modification of the protocol can execute
completely with the receipt of a message from the requesting site at
only one file server node.

      A parallel or striped file system provides parallel access to
data stored in many locations (referred to here as file server nodes)
in a parallel I/O system (1) or disk array (2).  Each individual
read or write operation may access data items located at several
different nodes.  These multiple-node accesses must be atomic to
provide consistent ordering of the various components of different
accesses.  When two accesses affect the same data and both span
multiple nodes, then at every node all components of one access must
either precede or follow all components of the other access.  In
general, in a message-passing computer or in a distributed computer
system, the interconnection network connecting the various file
server
nodes to each other and to the requesting sites may not guarantee any
absolute ordering of the access component messages received at each
file server node.  Therefore, a protocol is required to ensure
consistent
ordering of the access components at each file server node.

      Assume an array of file server nodes numbered from 0 to N-1.
Each file is distributed across some subset of these nodes.
Individual accesses do not necessarily span a contiguous range of
file server nodes.  Accesses to different files can be processed
independently of each other, with no concern for ordering of the
access components at each server node.  However, accesses made to the
same file may conflict with each other by accessing the same data
elements, and therefore some way of ensuring consistency atomicity is
required.  The consistency protocols presented here can be applied at
the file level, or can be applied among all accesses to all files
with no difference in the number of messages sent.  This choice is an
implementation question only.

      Each access is divided by the requesting site into its
component accesses such that each server node will receive either 1
or 0 messages (called an access component message) completely
describing the component of the access to be performed by that server
node.  Only those server nodes containing part of the requested data
will receive access component messages.  The access component message
sent to one server node is special...