I have an external SSD, as you know. I neglected to plug it in to my UPS, and we had a power outage last night. So my squeaky new fast boot drive was toasted. I could mount it, not repair it. "Read only." I reached back to my roots, and got a copy of DiskWarrior. Copied off what files I truly needed first (since I could see the drive), and then let DW do its stuff.
I'm back up and running. And GRATEFUL. I suspect if you've got an SSD and a Mac, you'll want DW sooner than later. Get it, just so you don't end up stuck like I was!
A side benefit - I'd worried about my internal HD. Seemed to be running hot, but noone online (forums) would give a reasonable temp. Everyone has an opinion on how hot a drive should run. Well, DW popped up a message, that basically said "This drive's frying itself." So now I will schedule in cracking my iMac to replace the internal.
So I was saved now, and saved in the future. That's a good investment. HIGHLY RECOMMENDED.