In 'Backup and Restore' page of Windows 7, when I click on 'Create System Image' in the left navigation pane, a window comes up and says "Creating a Shadow Copy". Could you please tell me:
1. What is a 'Shadow Copy'?
It is a point-in-time snapshot of the system, not a copy, so it is a misnomer. Copy on write is used. On a write , the old data that is going to be overwritten is first copied to the shadow copy area as a "diff" and the shadow copy references it instead of the new data (like an overlay). So data is copied, but only for writes that occur after the "shadow copy" was created. The file system at the time the shadow was made can be reconstructed from this "diff" data at any time by overlaying it over the file system, even though the file system has changed.
A clone can also be made of the whole system, but that doesn't make a lot of sense for backups or the system recovery "restore points". I don't know of any case where this is used - you wouldn't be able to access the system while it is copying like you can on copy on write.
2. Is it the same size as the system image or compressed?
It can be from zero length, if no changes have been made to the file system, to large if many have. It depends on your activity.
In a hidden system directory on the volume being shadowed.
4. Can I access this and transfer elsewhere for saving?
Since it is not a copy, but differences - only disk blocks that have changed, making a copy doesn't make sense.It is an growing set of changes to the fs and not a static copy.
Backups do make full copies of the file system, but by making a shadow copy "snapshot", then using it as the source, they can make a consistent point in time copy on a running system.
Macrium is good. I have never had it fail me and I have made dozens and dozens of restores