Re: Large block sizes support in Linux

On Mon, Mar 25, 2024 at 02:53:56PM +0100, Pankaj Raghav wrote:
> This is an excellent question that needs a bit of community discussion to
> expose a device agnostic value that userspace can trust.
> 
> There might be a talk this year at LSFMM about untorn writes[1] in buffered IO
> path. I will make sure to bring this question up.
> 
> At the moment, Linux exposes the physical blocksize by taking also atomic guarantees
> into the picture, especially for NVMe it uses the NAWUPF and AWUPF while setting
> physical blocksize (/sys/block/<dev>/queue/physical_block_size).
> 
> A system admin could use value exposed by phy_bs as a hint to disable full_page_write=off.
> Of course this requires also the device to give atomic guarantees.
> 
> The most optimal would be DB page size == FS block size == Device atomic size.

One other thing I remember is that some people modified the ZFS file
system parameters enough that they made Postgres non-durable and
corrupted their database.  This is a very hard thing to get right
because the user has very little feedback when they break things.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.