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[Vfs-info] An introduction to VFS
From: |
Hans van Buitenen |
Subject: |
[Vfs-info] An introduction to VFS |
Date: |
Fri, 18 Apr 2003 18:54:13 +0200 |
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Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020826 |
VFS
Virtual FileSystem
An Introduction to VFS
1.Table of Contents
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2.Intended audience 2
3.Introduction 2
4.Propersies of VFS, a short overview 3
5.Wat is the purpose of this FS? 3
6.Services 3
8.Demands on volume data 4
2. Intended audience
-----------------------------------------------------------------
This Introduction is intended for people interested in enhanced file
management in a no-nonsense fashion. It describes a way of managing
files in which quite a few all-day problems with managing files are solved.
This is primarily an Introduction to VFS that tries to give you a quick
overview of what VFS is. Anyone with some basic knowledge of computers
should be able to read it.
For more specific information you should read the URS.
3. Introduction
-----------------------------------------------------------------
Very briefly,
VFS is a filesystem that let's you manage ALL you files. Not just those
on disk, all of them! All your data also the data on tape, inside tar
files an data on CD can be added to your VFS directory whithout the need
to copy all the files to your harddisk.
From a technical point of view, VFS ia a database solution that
simulates an odinary directory structure.
So VSF is a Database oriented filesystem. You are not working in a
directory structure on disk but you are looking at a database that
reperents itself as a directory structure.
Althouh this FS might be usefull in environments with > 10 users it is
not intended for large user communities. It's main strength will come
forward in environments that have limitered IT support or none at all.
(SOHO environments)
4. Propersies of VFS, a short overview
-----------------------------------------------------------------
VFS can be compaired with a simple EDM system. The hart of VFS is a
"Directory database". This database discribes a directory structure
with files etc.
If a user moves files in this forder structure, then this is a change in
the database. The folder structure will be changed changed, not the
phisical location of all the files on disk. Files on disk will almost
never move. This is a important issue to understand, because VFS will
let you maintain (move, delete or change) files that are stored on
Read-only media.
Data can be stored on almost anything that is accessable by your system.
Harddisk
CD-Rom or DVD
nfs of smb mount
Every other blok device.
VFS is being designed for flexibility and ease of use.
Just like a Unix or Linux filesystem, VFS has just one folder tree.
In the contrarary to many databases, this system contains just one
folder tree that contains all folders and files. So to the user this
system behaves much like an ordinairy (Unix) directory.
The concept of a directory is used as a userinterface to data that can
be fisically stored anywhere.
5. Wat is the purpose of this FS?
-----------------------------------------------------------------
While working with files you are frequently confronted with all kinds of
bounderies that your'e not interested in as a system user. Such as:
Disk space.
Data on CD's or other offline media
Data inside (tar) archieves
Backup and restore files, finding files on backup media
VFS solves all these problems by using a virtual filesystem.
The undelaying media no longer limits the possibilities of maintaning
your data.
All available data will be managed inside a database that is being
represented as one directory.
Only after the data inside a file is needed, VFS will ask for a volume
(CD) if this file is not available online.
A file, regardless what media it is on, can simpely be edited and filed.
VFS will create a new file version inside a volume on a local disk.
VFS looks at a CD as a normal data volume. All backuped files are
visible whithin VFS, simpely inside their directory.
6. Services
-----------------------------------------------------------------
VFS will monitor what files need to be written to a backup.
Disk cleanup gets an extra demension when using VFS. If a disk starts
filling up, VFS can decide to start deleting older and unused files that
are also on your backup media
7. Backup's
-----------------------------------------------------------------
VFS is based on a backup strategie that uses incremental backup's only.
The backup media (CD's) are filled with new or changed files only. Since
no CD's are ever to be wasted, all older file versions are always available.
Benefits of this backup strategy are:
You don't need expensive backup hardware that can contain all your disk
data. A 650 Mb CD-RW is all you need. This is much smaller than the
current available disk sizes.
The quantity of data in your VFS directory may grow a lot bigger than
your phisical disk size.
You don't need to make time consuming full backup's.
You never overwrite old data, all old file versions are still available.
Finding old versions is simple, all versions are just displaysed all in
one place.
You never need to browse a CD to search for a file. VFS will ask for the
right CD and locate your file.
Managing files is as simple as using a directory structure. But with
VFS, if you reorganize a directory, all you files (also the ones on your
CD's) will follow these changes. Because a VFS user looks into the
database He or she will only see the updated directory structure.
Disadvantages
This way of working has it's geatest benafits in a "home" situation. If
a company has expensive tape robots then part of the advantages will not
count for them.
8. Demands on volume data
-----------------------------------------------------------------
There are not any specific demands on volume data.
One of the requirements is to be able to add (import) old backup media
(CD's) whithout the need to rewrite them.
Data locations with a directory structure are permitted
Tar files can be added with all separate files inside them.
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