RE: [PoC] Non-volatile WAL buffer

From: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
> It's interesting that they only place the tail of the log on PMEM, i.e.
> the PMEM buffer has limited size, and the rest of the log is not on
> PMEM. It's a bit as if we inserted a PMEM buffer between our wal buffers
> and the WAL segments, and kept the WAL segments on regular storage. That
> could work, but I'd bet they did that because at that time the NV
> devices were much smaller, and placing the whole log on PMEM was not
> quite possible. So it might be unnecessarily complicated, considering
> the PMEM device capacity is much higher now.
>
> So I'd suggest we simply try this:
>
> clients -> buffers (DRAM) -> wal segments (PMEM)
>
> I plan to do some hacking and maybe hack together some simple tools to
> benchmarks various approaches.

I'm in favor of your approach. Yes, Intel PMEM were available in 128/256/512 GB when I checked last year. That's more than enough to place all WAL segments, so a small PMEM wal buffer is not necessary. I'm excited to see Postgres gain more power.

Regards
Takayuki Tsunakawa