Question: Is it safe to de-fragment your disk when you have low disk space? What could be the consequences? What are the advantages and disadvantages of de-fragmenting. Is it possible to resume de-fragmentation of a disk after a few days? Can de-fragmentation of large disks be simplified as it takes lot of time to complete? Is it possible to lose data after de-fragmentation? Will it reclaim my Disk-space?

Answer: 
" Is it Safe to De-fragment your Disk when you have low disk space, what could be the consequences?"

The defragmenter will not complete the defrag efficiently if you have low free space if you use the Windows defragger. But you can run a third party automatic defragger which defrags under less than 5% free space and get the job done without any problems.

"What are the Advantages and Disadvantages of De-fragmenting.Is it Possible to resume de-fragmentation of a disk after a few days. can De-fragmentation of large disks be simplified as it takes lot of time to complete. Is it possible to lose data after de-fragmentation. Will it reclaim my Disk-space."

There are no disadvantages, advantages are that the performance will be smooth and data access fast.
With intelligent automatic defrag technology it's also possible to have a program defrag in the background without being resource intensive and will also defrag very fast as compared to the built-in program. Defrag doesn't create any new diskspace and there is no risk of data loss. Just ensure that you have a power backup for the PC.
I only had defrag data loss one time in my life, it was because I had low disk space and tried to cancel the defrag because it was so slow, unfortunately it corrupted a critical system file, but like I said this only happened to me once in thousands of defrag routines. Defrag does not reclaim any disk space, it just consolidates the files on the hard drive. You need to do a disk clean up to gain disk space.

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