Re: PITR, checkpoint, and local relations

> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org
> [mailto:pgsql-hackers-owner@postgresql.org]On Behalf Of Tom Lane
> Sent: Friday, August 02, 2002 5:25 PM
> To: J. R. Nield
> Cc: Richard Tucker; Bruce Momjian; PostgreSQL Hacker
> Subject: Re: [HACKERS] PITR, checkpoint, and local relations
>
>
> "J. R. Nield" <jrnield@usol.com> writes:
> >> (In particular, I *strongly* object to using the buffer manager at all
> >> for reading files for backup.  That's pretty much guaranteed
> to blow out
> >> buffer cache.  Use plain OS-level file reads.  An OS directory search
> >> will do fine for finding what you need to read, too.)
>
> > How do you get atomic block copies otherwise?
>
> Eh?  The kernel does that for you, as long as you're reading the
> same-size blocks that the backends are writing, no?
If the OS block size is 4k and the PostgreSQL block size is 8k do we know
for sure that the write call does not break this into two 4k writes to the
OS buffer cache?
>
>             regards, tom lane
>
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