I am the IT Manager for a small solicitors' firm and we need a
back-up, LAN, Human Failure recover solution. There are 7 Windows XP
PCs, 2 Freecom Network Drives and a simple LAN with USRobitic Routers.
The users currently share files on Drive N: with a total size of
around 800MB and 80,000 files.

I want to guard the system against:

a) hardware failure of one drive
b) LAN failure
c) human error 


Below is one solution that I think would fit the above needs,

I have some questions that need answering:
 
1. Is this the best way of achieving this, and how do I do it? 
 
2. which is the best software, and how much is it going to cost - I
have already investigated Avail (rediculously expensive and
ineffective) and mobiliti (better but not perfect as there is no guard
against human error or automatic switching to the F: drive, see
below)?
 
3. How much resources will the server software use on the controlling
PC, i.e. will a dedicated one be needed?

4. The ease of recovery is my biggest concern, I am off-site and there
is little IT knowledge on-site, I currently provide remote control
support, but if the network fails that is obviously impossible)
therefore recovery needs to be pretty much automatic).

5. The cost of the whole system should be less than $1000, though hopefully less.

So here goes... 

LAN Failure Coverage
the users work from the workstation's hard drive (C: drive) whilst all
changes they make there are real-time copied bi-directionally to drive
N at the bit-level: This means that if User A makes a local change,
via the N: drive, all the other C: drives will be immediately updated
with that change, so that all users constantly have the same files,
and writes issues remain resolved (i.e. read-only for already opened
files). This would guard against LAN failure as they could still
access the files (as they were at the time of the failure). I would
like the system to automatically update with changes that occurred
when the LAN was down, on reconnect (with rules for files with more
than one version (although this is unlikely). I would also like the
user to be warned that they are working offline (i.e. with a network
failure) so that they can connect me so that I can restore it. This
warning needs to be obvious, such as a pop up message.
 
Hardware failure
Drive F would be set to mirror drive N, in the case of drive N
failing. I need the system to automatically switch to F, as if it were
the N drive in this event, so that the C: drives carry on being
synchronised and backed up.
 
Human Error
There is a need to guard against accidental deletions and file
changes, The users need to be able to easily restore a previous
version of a file. The time increments need to be close together,
hourly at least.

You must answer these questions fully, not: 'this might work' and have
seen the solution you propose work in a similar scenario, preferably
installed it yourself. 

Please ask for clarification if you are not sure what I mean at some point.

Thanks in advance,

Will