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the cow approach likely plays better with flash based storage since rewrites happen less often. so if you've got a lot of otherwise extra storage then maybe it
by simcop2387 6y ago
the cow approach likely plays better with flash based storage since rewrites happen less often. so if you've got a lot of otherwise extra storage then maybe it's a good idea. though if you run on top of something like f2fs maybe it'll be better in that respect than pg does on it's own.
- jeltz 6y agoIn theory, yes, but PostgreSQL's current storage is not optimized for flash.
- jabl 6y agoIIRC one issue with the current design is that as new rows are written in a different place, all indexes on that table have to be updated as well, leading to write amplification. If you do an update in place, you don't need to modify indices (but now that I think of it, what about concurrently running transactions that might want to read the old values using the old indices...?) Also during the vacuum there's a lot of writes marking rows as available.