...it has its own Linux based...
...Anyway, I read that ext3 is only an overlay to the LVM structure...
LVM is the linux logical volume manager. Physical volumes are added to a volume group, and then logical volumes are created from the volume group. Thus it aggregates multiple physical devices (disks or arrays, or any combination thereof), and allows that space to then be divvied up however you want into logical volumes. Those logical volumes are "virtual" but they are still treated as block level devices. That is you specify a size for them, and you can format them NTFS, JHFS+ or in this case one of the linux native filesystems, ext3.
Another feature of LVM is the snapshot, which allows you to create another instance of a volume. The original instance can remain mounted read-write, and continue to be used/modified. The 2nd instance, the snapshot, will be frozen in time and will not be modified at all.
So LVM is a volume manager. And Ext3 is the file system, analogous to NTFS or JHFS+. However, Ext3 is not a file system that I'd expect any Windows or Mac OS based file undelete or recovery program to have any idea what to do with. And in fact it's rather tedious and complicated
to do file recovery on ext3 even within linux natively.
specially since this OS server is shared access, I can't do much as to accessing mounted drives.
Well, there are many ways to go about this: telnet or ssh is included on even 1MB firmware for wireless routers I use, so I'd think your RAID box likely has one or both. But getting ext3grep installed is non-trivial, but possible. That's the best bet. It is possible to take the drives out, installed in a PC, boot the PC from a linux Live CD, manually assemble the RAID, and then use the Live CD's package manager to install the latest and greatest ext3grep (even though it is a LiveCD it uses memory as a virtual disk so you can install software packages booted from a LiveCD, they of course vanish upon reboot or shutdown).
If I can't have a way of undeleting that file, I will be dumping everything off the 4TB and then installing WinHomeServer which I have a copy of..(I was considering FreeNAS).
Then move the content all back on.
I don't understand what this means. Installing these things on what? This Intel box? Do you realize the stock box has 512MB of RAM and no video port? I don't understand what this is about.
Just to be clear, the array is perfectly fine. As I said, I simply deleted a file I want to retrieve. Nothing failed, nothing stopped working.
Yeah I understand. But you seem to think that deleting a file is a simple event, as is undeleting it. File systems are not at all designed with this in mind. Any possible recovery is purely incidental to what they were designed to do, which is actually to reuse freed up disk sectors relatively quickly. It is much more difficult recovery deleted directories than it is recovering deleted files.
There is one other possibility here, which is maybe the logical volume can be exported read-only via iSCSI. And then with the SmallTree free iSCSI initiator (think it's still free), you can then point a conventional file recovery program to that disk and have it start scanning sector by sector for familiar patterns, i.e. images and documents. It will not understand the file system, but such utilities can frequently find files based on their content's pattern. The caveat is files often aren't in one continuous set of sectors, they can strewn all over the disk (fragmentation), so the files may be useless or difficult to get the various pieces located and then concatenate them together.
I hope some details above can help someone see a option.
Do a google search for ext3grep and see if this is way outside your realm of interest level. If it is, you will either need professional data recovery service, or abandon this data.