Message-ID: <4560FE27.5050600@modgraph-usa.com>
Date: Sun, 19 Nov 2006 17:00:23 -0800
From: "Craig A. James" <cjames@modgraph-usa.com>
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To: Michael Stone <mstone+postgres@mathom.us>,
	pgsql-performance@postgresql.org
Subject: Re: Postgres server crash
References: <19583.1163700841@sss.pgh.pa.us>
	<Pine.LNX.4.33.0611181713170.19262-100000@denzel.in>
	<20061119184105.GC2366@mathom.us>
	<4560D6B1.8060306@modgraph-usa.com>
	<20061119223236.GE2366@mathom.us>
In-Reply-To: <20061119223236.GE2366@mathom.us>
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> You realize that it had to be turned on explicitly on IRIX, right? But 
> don't let facts get in the way of a good rant...

On the contrary, with Irix 4 and earlier it was the default, but it caused so many problems that SGI switched the default to OFF in IRIX 5.  But because it had been available for so long, many important apps had come to rely on it, so most sites had to immediately re-enable virtual swap on every IRIX 5 server that came in.  Admins just got used to doing it, so it became a "default" at most sites, and admins often couldn't be convinced to disable it for database server machines, because "That's our standard for IRIX configuration."

I worked at a big molecular modeling/visualization company; our visualization programs *required* virtual swap, and our server programs *prohibited* virtual swap.  Imagine how our sales people felt about that, telling customers that they'd have to buy two $30,000 machines just because of one kernel parameter.  Of course, they didn't, and our server apps took the heat as being "unreliable."

SGI called it "virtual swap" which I always thought was a hoot.  You have virtual memory, which is really your swap space, and then virtual swap, which is some kind of dark hole...

Craig