Persistent Memory Redundancy?

Mike Texter

4/20/24, 2:14 PM

This is the first time I've really dug into PMMs (Intel Optane), so bear with me if I'm a little slow on the uptake. It looks like you can configure these in either cache- or disk-mode, depending on your system. As one who wants to add disk-mode PMMs to their environment but has concerns about redundancy, what happens in the event of a PMM failure? It seems as though there's no way to set up something akin to a hardware RAID for PMMs, but is there any other way to get redundancy at the hardware level? The only options I've found are software-based, which doesn't seem great. System in question is a DL360 Gen10.

Quickspecs mentions nothing: https://www.hpe.com/psnow/doc/a00008159enus.pdf

Other HPE memory guides mention nothing: https://www.hpe.com/psnow/doc/a00017079enw

Configuration tutorials on youtube mention nothing. https://www.youtube.com/watch?v=AqqymYPAfWk

What would be a use case for PMMs in disk mode? Am I missing something?

This doc from Intel says hardware-based redundancy is not possible: https://www.intel.com/content/www/us/en/developer/articles/technical/speeding-up-io-workloads-with-intel-optane-dc-persistent-memory-modules.html

Cheers,

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TomTom

4/20/24, 2:22 PM

what happens in the event of a PMM failure

It is gone. If wou want redundancy, set up redundancy (i.e. RAID 1)

The only options I've found are software-based, which doesn't seem great

Why? Mirroring is trivial on the CPU - just submit a write command for the same data to both endpoints. Software is WAY better for that use case than hardware.

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