I see various issues raised but not properly addressed
1. we would need to drop support for segment sizes < 16MB unless we adopt a new incompatible filename format. I think at 16MB the naming should be the same as now and that WALfilename -> LSN is very important. For this release, I think we should just allow >= 16MB and avoid the issue thru lack of time.
2. It's not clear to me the advantage of being able to pick varying filesizes. I see great disadvantage in having too many options, which greatly increases the chance of incompatibility, annoyance and breakage. I favour a small number of values that have been shown by testing to be sweet spots in performance and usability. (1GB has been suggested)
Does the options 16, 64 and 1024 seem good.
We can remove sizes below 16 as most have agreed and as per the discussion, 64MB and 1GB seems favoured. We could probably allow 32MB since it was an already allowed size?
3. New file allocation has been a problem raised with this patch for some months now.
This did not seem to be an open issue, at least there was not many disagreements. Higher the server load, more WAL generated. For the same load, the frequency of file allocation reduces for higher wal-segsize values. Overall it is either filling up many files or few larger files.