Sometimes two is none.
Warning: computer geekery.
I got a call last night from one of my partners. The electrical power to our entire building went down for about 9 hours yesterday. This resulted in a less than graceful shutdown of a dozen servers.
We office in a very upscale part of town. The electrical infrastructure is almost third world. :(
When access to the server backup image requires access permission authentication to the server that is toasted you have what is known as a conundrum.
I have a backup image of the server.
I cannot get to the image of the server.
This is because the device storing the server image wants to check my access credentials with the server that is missing*...the server for which it holds the backup image. Therefore, backup storage device is inaccessible.
Fortunately my redundancies have redundancies. Were it not for the secondary domain controller, we would not have been able to work today. This would have been very bad. North of $10k per hour billable lost.
We have expensive high fallutin' backup software. I have seen this software fail to make backups frequently. So, I have a backup backup, aka as an MS Dos batch file that launches via the task scheduler and has yet to fail.**
I see now that I need to add the domain controller backup image files to that MS DOS Batch file routine for events like this, so it is somewhere that I can get to under almost any circumstances.
If you can't get to your backup, it might as well not be there.
* for those that know of such weirding ways, it
was a virtual machine that is now listed as "inaccessible guest" or some such helpful information on the host server.
** The MS DOS xcopy command is your friend. Believe it or not, MS DOS still exists in Windows 7. I'm not sure about Windows 8. If not, I'm never
upgrading to Windows 8.