Обсуждение: postgres block size alignment with filesystem block size

Hello, I am setting up a new postgres production server in a managed hosting environment.  I dont have much insight into the underlying disk architecture but the filesystem I have been presented with has a 4k block size.  Postgres defaults to 8k block size; would it be beneficial to repave the filesystem at an 8k block size or problematic to leave it at 4k?   I have seen posts suggesting alignment of the postgres block size and the file system block size and the raid block size, but wonder if a multiple is sufficient or if it should match exactly.

Mike Broers <mbroers@gmail.com> writes:
> Hello, I am setting up a new postgres production server in a managed
> hosting environment.  I dont have much insight into the underlying disk
> architecture but the filesystem I have been presented with has a 4k block
> size.  Postgres defaults to 8k block size; would it be beneficial to repave
> the filesystem at an 8k block size or problematic to leave it at 4k?

I doubt it's worth the trouble to change it.  Most filesystems default
to 4k or smaller block sizes, so that's what PG is accustomed to run on.
I think it would only really be an issue if PG's block size weren't a
multiple of the filesystem block.

            regards, tom lane

On Wed, Jun 06, 2012 at 12:24:35PM -0400, Tom Lane wrote:
> Mike Broers <mbroers@gmail.com> writes:
> > Hello, I am setting up a new postgres production server in a managed
> > hosting environment.  I dont have much insight into the underlying disk
> > architecture but the filesystem I have been presented with has a 4k block
> > size.  Postgres defaults to 8k block size; would it be beneficial to repave
> > the filesystem at an 8k block size or problematic to leave it at 4k?
>
> I doubt it's worth the trouble to change it.  Most filesystems default
> to 4k or smaller block sizes, so that's what PG is accustomed to run on.
> I think it would only really be an issue if PG's block size weren't a
> multiple of the filesystem block.

I have heard about performance issues when the virtual machine block
size isn't aligned with the host OS block size.

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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
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