(How) Can I repair this drive?  

I had a power outage while I had several processes involving one 4 TB drive in my system.

When power came back on and I ran chkdsk on all the drives in my system, I got the following for this one drive:



What does the chkdsk insufficient disk space error message mean? The total drive space (formatted) is 3.63 GB and 2.39 GB is free space. Can I address this issue by deleting some non-critical files on this drive?

There is are two critical folders on this drive that I really want to save by copying off to another drive. One of these folders contains just over 2,000 files, different sizes. After a few seconds, copy speed drops to between 375 KB/sec on 0 KB/sec. Normal copy speed on my system between 2 HDDs is over 100 MB/sec. This seems hopeless to me.

My system is old, but does have PCI-E 3.0 architecture.

Is this drive a total goner, and I have to reformat the entire drive to get back the use of this drive. Before this power outage, HD Sentinel Pro reported this drive as Perfect.

Later on, consider using an UPS. When power suddenly goes out, you have just enough time to stop any copy or move operations, save any work in progress, and shutdown gracefully.
Right now, continue data recovery mode, can HDD be added to another computer for possible access?
And, are data backups on external media in existence, and if so, current?

RolandJS said:

Later on, consider using an UPS. When power suddenly goes out, you have just enough time to stop any copy or move operations, save any work in progress, and shutdown gracefully.
Right now, continue data recovery mode, can HDD be added to another computer for possible access?
And, are data backups on external media in existence, and if so, current?

Yes, a UPS is an option. Thing is, around here, power blackouts are extremely rare. The drive is fully accessible in my desktop system. The irony is, this drive is a backup drive. It is "external media" in the sense that every year I change out my backup drive for a new one, and then I store the old drive in anti-static bag in a drawer.

I'm wondering if there are any tools that are better than chkdsk, or can fix the extremely slow copy speed.