[Vfs-info] An introduction to VFS

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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
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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
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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
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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?
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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
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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
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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
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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.