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Comment by eqvinox | Hacker News Reader

Making them write-once doesn't increase the capacity; that's mostly limited by how many analog levels you can distinguish on the stored charge, and how many cells you can fit. The management overhead and spare capacity to make SSDs rewritable is –to my knowledge– in the single digit percentages.

(Also you need the translation layer even for write-once since flash generally doesn't come 100% defect free. Not sure if manufacturers could try to get it there, but that'd probably drive the cost up massively. And the translation layer is there for rewritable flash anyway... the cost/benefit tradeoff is in favor of just living with a few bugged cells.)

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I suspect that hawki was assuming that a WORM SSD would be based on a different non-flash storage medium. I don't know any write once media that has similar read/write access times to an SSD.

FWIW, there are WORM microsd cards available but it looks like they still use flash under the hood.

I don't know enough specifics, so I didn't assume anything :) In fact I was not aware of non-flash SSDs.

Because of the Internet age there probably is not much place for write once media anyway, even it would be somewhat cheaper. But maybe for specialized applications or if it would be much much cheaper per GB.

The only write once media I'm aware of that is in significant use are WORM tapes. They don't offer significant advantages over regular tapes, but for compliance reasons it can be useful to just make it impossible to modify the backups.

What about EPROMs? I mean could those be scaled down with 7nm lithography to be energy efficient incorruptible fast storage?

You mean the UV erasable kind? Essentially phase change memory? Very hard to miniaturize?

Because the older Flash aren't as stable when miniaturized as you'd expect. Current flash is a direct descendant of these, they only are more stable because the cells are much chunkier and thus with lower leakage.

I was thinking of the anti-fuse based PROMs not EPROMs sorry. I figure if you miniatures those they'd be faster and denser and use-based fully reliable.

I thought along that route as well but I'm not sure how the feature scale of a fuse compares to the size of a flash cell - especially since the latter can contain multiple bits worth of info (MLC). Assuming the fuse write results in a serious physical state change of some sort, I suspect that the energy required for high speed writes (at SSD speeds) may become substantial.

That being said, it's not clear how innovation has occurred in this direction in the storage space.

> Making them write-once doesn't increase the capacity

It could theoretically make them cheaper. But I guess that there wouldn't be enough demand, so you'd be better off having some kind of OS enforced limitation on it.

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