Re: The FAQ on fsync/O_SYNC

[Gian-Carlo Pascutto <gcp@sjeng.org>]

On 20-04-15 06:27, Zygo Blaxell wrote:

>> I'm curious as to whether +C has any effect on BTRFS's durability, too.
> 
> I would expect it to be strictly equal to or worse than the CoW
> durability.

In addition to the stuff pointed out, I've wondered about this:
PostgreSQL full_page_writes copies 8k pages in order to prevent
corruption from partial writes. But btrfs has 16k pages by default, so a
corrupted FS page would corrupt more data than PostgreSQL protects.

Maybe it's not an issue if the underlying HW has 512b/4k sectors, or
maybe I'm misunderstanding what the respective features assume, but
unless informed to the contrary I wouldn't be entirely comfortable with
this.

(With CoW enabled, you don't have partial writes, so the point is moot)

-- 
GCP