Browse Prior Art Database

Local Cache for Server Files

IP.com Disclosure Number: IPCOM000104232D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 152K

Publishing Venue

IBM

Related People

Bolen, D: AUTHOR [+4]

Abstract

Disclosed is a cache based file system, called Local Cache for Server Files (LCSF), that caches files accessed from a server onto a user's local hard disk. It decreases the number and time for server file accesses significantly and also provides server independence in case of server or network faults. It makes server files virtually portable. It keeps track of server file updates and gives the latest version of the file to the user. It is ideally suited for an ordinary user as well as an administrator, as it has two write back options that update files on the server when they are modified in the cache. It has its own Installable File System (IFS). It allows shadowing of multiple servers from one master server, thus decreasing maintainance efforts in a multiple-server environment.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 37% of the total text.

Local Cache for Server Files

      Disclosed is a cache based file system, called Local Cache for
Server Files (LCSF), that caches files accessed from a server onto a
user's local hard disk.  It decreases the number and time for server
file accesses significantly and also provides server independence in
case of server or network faults.  It makes server files virtually
portable.  It keeps track of server file updates and gives the latest
version of the file to the user.  It is ideally suited for an
ordinary user as well as an administrator, as it has two write back
options that update files on the server when they are modified in the
cache.  It has its own Installable File System (IFS).  It allows
shadowing of multiple servers from one master server, thus decreasing
maintainance efforts in a multiple-server environment.

      LCSF consists of an Installable File System (IFS) and a Cache
Module.  A user refers to a LAN server or NFS (or any such server) by
a drive letter.  We refer to such a drive as the network drive.  This
drive letter can be attached (i.e., mapped) to a virtual drive
letter, using one of LCSF's commands.  From then on, instead of
referring to server files using the LAN or NFS drive, the user can
refer to them using the attached virtual drive.  The advantage of
doing so is that the cache module keeps track of the frequency and
nature of the way the user accesses each file, and caches each file
based on a variation of the Least Recently Used cacheing algorithm.
When the user makes a file request on any drive, the OS/2* kernel
redirects the request to LCSF's IFS if the request was made on an
attached virtual drive.  The IFS checks what kind of request was
made.  It replaces the virtual drive specification with the actual
network drive and except for a directory request (e.g.,
DosFindFirst), or a file-close request (e.g., a DosClose), or a
file-open request (e.g., a DosOpen), it directly performs the
requested operation on the network drive.  In doing so, it actually
requests the OS/2 kernel to perform the operation, which in turn
might redirect the operation to a different File system, like the
LANServer or NFS.  However, if the request is one of the three types
mentioned above, then LCSF's IFS does the following:

1.  File Open requests :

    In case of a DosOpen request, the IFS signals the cache module.
    The cache module in turn first searches its cache table to
    determine if the required file is present in the cache.  If not,
    it first copies the file from the server to the cache, renames
    the file using its own customized algorithm, marks the file as
    hidden and system and, if the file is an executable file, it also
    encrypts the first two bytes of the file.  All this is done so

    that a user cannot directly go into the cache and access the
    files.  He/she has to go via LCSF's IFS.  The cache module then
    returns control back to the IFS w...