A customer recently asked me if they should use the spare HDD (Hard Disk Drive) in their computer to create an image of their C drive periodically, or should they mirror the C drive partition.
Note that the OS (Operating System) Boot and System files must be on the same partition!
Mirroring the HDD (Hard Disk Drive) is also known as RAID 1. “RAID” stands for Redundant Array of Inexpensive (Independent) Disks. This is a way to provide redundancy of your precious data. Mirroring works in real time and backs up your whole C drive on the fly behind the scenes.
Microsoft has an easy and convenient way to mirror a drive via the Disk Management system.
Microsoft also offers a back up solution called “File History”. The caveat is that it only backs up your files; rather than programmes. You can only use this to restore deleted files. If your HDDs fail then you would need to reinstall all of your programmes and OS from scratch!
Here are the pros and cons:
A mirrored drive is a perfect copy of the C drive. Which means if the C drive fails, the mirrored drive can be used to get the computer back up (pun intended) and running very quickly. The mirrored drive will be instantly up to date because both drives are written to simultaneously. The mirrored drive cannot be smaller in storage size than the C drive partition.
The cons are that if a file is deleted on the C drive, that same file is immediately deleted on the mirrored drive. Unless you have separately backed up the file, then that file is lost forever.
An image of the C drive can be used to restore the computer back to the date that the image was taken. This involves much more work than using a mirrored HDD. You can also mount the image to recover individual files should the need arise. Note that you should attempt to image your drive weekly as you will lose any information that was added after your last image. Microsoft provides an easy way to image your drive via the back up tool which you can access via the Backup icon in the Control Panel.
With a mirroed drive, please bear in mind that if your motherboard fails, then unless you replace the motherboard with exactly the same make & model, there is a good chance that the mirrored drive cannot be used to boot the computer and you would have to use tools to view the files on the mirrored drive to recover them.
Finally, I have discovered a bug in the Microsoft disk mirroring tool. If your second HDD is EXACTLY the same size as the C drive partition, you will get an insufficient disk space error message when you try to mirror the C drive partition. To correct this, simply decrease the space on C partition by 10MB using the disk management tool.
To be honest, the best solution would be to have three extra HDDs. Two would be external USB HDDs to store images on and the third an internal HDD to functon as a RAID 1.
Another reason to store an image on an external drive is so that you can store it offsite should anything happen to your computer or where the computer is located.