Re: Optane Flameout?
@Liam Proven:
After reading the article, I thought, "Neat use of Optane. But isn't Optane some kind of fast flash memory? [I didn't know the particulars of Optane] Is it subject to write-cycle wear, as is flash memory? I should find out."
I then DuckDuckGo'd Optane wear-levelling and got Intel's explantion of Optane wear-levelling, which I partially-reproduced in my comment. If you go to the URL I listed, you will see a large-font headline reading, "Protect the Lifespan of Your Intel® Optane™ Solid State Drive".
After reading Intel's article, I naturally came to the conclusion that write-cycle wear on Optane is a significant issue.
Whether Optane is installed into a quasi-drive, or in DIMMs does not alter the underlying technology; both forms will share the same limitations, flaws, etc.
Thus, I wondered whether dm-pcache had a [hopefully-optional] policy which would leave some cache memory (whether pseudo-disc or pseudo-RAM) unused, so that Optane-used-as-cache could properly wear-level itself.
You asked why a cache failure would be a problem.
The problem is that corrupt data can replace your "good" data living on permanent storage.
This would happen is if the data were corrupted in-cache, after a write-to-disc command had been issued by a user's program, yet before the data had actually been copied from the cache to the disc.