Comment by ChuckMcM

7 years ago

This is sad, I know that one large user of Linux found this problem in 2009 or so and fixed it for the version of Linux they used in their fleet of servers. I am surprised it didn't make it upstream from then.

8 comments

ChuckMcM

beering 7 years ago

I don't know if it's the same person, but someone working on Atlassian's cloud offerings said he reported this issue (along with a working patch) to Postgres and they declined it. Sounds like what they do for cloud services is run a lot of Postgres instances where the DB data is on a big NFS, and this bug was a bigger problem due to how NFS works. But after patching the fsync handling in Postgres, they continued using Postgres-on-NFS with great success.

Unfortunately I can't find the original comment, but I think it was on another HN story about Postgres+fsync.

Edit: I found it: https://news.ycombinator.com/item?id=19126601 and I may or may not have hallucinated the part about Atlassian.

pgaddict 7 years ago

I think it's a bit strange to claim the PostgreSQL community just declined the patch. Just look at the thread on pgsql-hackers list:
https://www.postgresql.org/message-id/flat/46ED7555-9383-45D...
As anarazel already pointed out in the hackernews thread you linked, there's one person who was initially skeptical about the patch, and a couple of people chimed in with feedback (e.g. pointing out some mount options may fix it, which I think is valuable). And then the author of the patch just disappears from the discussion, so the thread kinda gets forgotten for a couple of months.
I'm sure PostgreSQL community has its flaws, but I doubt this is a particularly clear example ...
dboreham 7 years ago
In case someone reads this and gets the impression that running PG over NFS is in general safe or a good idea, I'm pretty sure it still isn't, unless like the OP you have a complete understanding of what you're doing.
- rosser 7 years ago
  
  I have quite successfully run pg atop NFS — even, in limited, point-solution type roles, in production. My experience doing that didn't leave me with the impression that it was a particularly egregious thing to do, though I would definitely take many, many additional steps to ensure redundancy and availability if I were going to use it more generally.
  You're right though: you really do want to have some idea what you're doing, if you're going to go there.
  Source: my day job is PostgreSQL DBA, and has been for ~15 years now.
  EDIT: Phrasing.
  
  2 replies →
- merb 7 years ago
  
  OT: it depends on how much writes/reads you get. for most people nfs is probably an easier solution for HA on postgres than anything else.
- georgebarnett 7 years ago
  
  That’s pretty much computing. It’s usually the case that unless you have a complete understanding, there’s a pothole waiting to trip you.
  As an FYI - we no longer use Postgres on NFS as we have migrated the entire architecture underlying the systems in question.