Re: Re: Synch Rep: direct transfer of WAL file from the primary to the standby

Hi,

On Wed, Jul 8, 2009 at 12:49 AM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> This design seems totally wrong to me.  It's confusing the master's
> pg_xlog directory with the archive.  We should *not* use pg_xlog as
> a long-term archive area; that's terrible from both a performance
> and a reliability perspective.  Performance because pg_xlog has to be
> fairly high-speed storage, which conflicts with it needing to hold
> a lot of stuff; and reliability because the entire point of all this
> is to survive a master server crash, and you're probably not going to
> have its pg_xlog anymore after that.

Yeah, I agree that pg_xlog is not a long-term archive area. So, in my
design, the primary server tries to read the old XLOG file from not only
pg_xlog but also an archive if available, and transfers it.

> If slaves need to be able to get at past WAL, they should be getting
> it from a separate archive server that is independent of the master DB.

You assume that restore_command which retrieves the old XLOG file
from a separate archive server is specified in the standby?

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center