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Comment by floatboth | Hacker News Reader

ZFS developers like to do this with hard drives :) But how did IBM do that with RAM? Do mainframes have… redundant RAM? Like literally sticks mirroring others?

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Apparently, they can. https://en.wikipedia.org/wiki/Redundant_array_of_independent...

But that was only introduced in 2010, so either the timeframe I was guessing at is wrong, or I'm misremembering what component it was. Could have been disk drives maybe.

I have seen one PC-based server that had redundant RAM. I never tried pulling out RAM modules, but I guess there is not much point in having a RAID1-like arrangement for RAM if the machine cannot handle random RAM modules dying without crashing the OS. And it wasn't even a super high-end system.

> I have seen one PC-based server that had redundant RAM

Yes, I've seen this too, and on lowish-end servers.

Memory mirroring is a pretty common feature on basically every x86 server I've used (going back to the Core 2-based Xeon's, no experience with older platforms), though I've never tried just yanking DIMM's out and wouldn't recommend trying it.

See [0] for an example of how people who are serious about fault tolerance design things.

[0] https://en.wikipedia.org/wiki/Tandem_Computers

Yes.

Doesn't help when your mainframe's infiniband controllers shit the bed and take the whole box down (a thing which has happened to me).

Yes.

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