Re: Weird XFS WAL problem

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Greg Smith" <greg(at)2ndquadrant(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>
Cc: "Craig James" <craig_james(at)emolecules(dot)com>, "Matthew Wakeling" <matthew(at)flymine(dot)org>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Weird XFS WAL problem
Date: 2010-06-04 15:16:41
Message-ID: 4C08D2890200002500031F54@gw.wicourts.gov
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Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> On another topic, I am a little unclear on how things behave when
> the drive is write-back. If the RAID controller card writes to the
> drive, but the data isn't on the platers, how does it know when it
> can discard that information from the BBU RAID cache?

The controller waits for the drive to tell it that it has made it to
the platter before it discards it. What made you think otherwise?

-Kevin

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