[Mail Delivery System ] Mail delivery failed: returning message to sender

Incidentally, Tom, you seem to be using a pretty bogus blackhole list that
includes blocking static address assignments based on the DNS records. I doubt
this achieves much in the way of spam filtering, but it's preventing you from
getting my mails. (Perhaps that's a good thing)


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To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Greg Stark <gsstark@mit.edu>,  pgsql-hackers@postgresql.org
Subject: Re: [pgsql-hackers-win32] [HACKERS] win32 performance - fsync question
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From: Greg Stark <gsstark@mit.edu>
Organization: The Emacs Conspiracy; member since 1992
Date: 24 Feb 2005 13:34:36 -0500
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Tom Lane <tgl@sss.pgh.pa.us> writes:

> Greg Stark <gsstark@mit.edu> writes:
> > I'm a bit surprised that the write-cache lead to a corrupt database, and not
> > merely lost transactions. I had the impression that drives still handled the
> > writes in the order received.
>
> There'd be little point in having a cache if they did, I should think.
> I thought the point of the cache was to allow the disk to schedule I/O
> in an order that minimizes seek time (ie, such a disk has got its own
> elevator queue or similar).

If that were the case then SCSI drives that ship with write caching disabled
and using tagged command queuing instead would perform poorly.

I think the main motivation for write caching on IDE drives is that the IDE
protocol forces commands to be issued synchronously. So you can't send a
second command until the first command has completed. Without write caching
that limits the write bandwidth tremendously. Write caching is being used here
as a poor man's tcq.

--
greg




--
greg