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From: tmh@prosun.first.gmd.de (Thomas Hoberg)
Newsgroups: comp.unix.sysv386
Subject: Re: out of swap space??
Message-ID: <641@bigfoot.first.gmd.de>
Date: 7 May 91 17:01:03 GMT
References: <1991Apr23.214037.16410@netcom.COM> <1991Apr24.123035.4193@virtech.uucp> <455@jgaltstl.UUCP>
Sender: news@bigfoot.first.gmd.de
Reply-To: tmh@prosun.first.gmd.de (Thomas Hoberg)
Organization: GMD-FIRST, D-1000 Berlin 10
Lines: 46

In article <455@jgaltstl.UUCP>, terry@jgaltstl.UUCP (terry linhardt) writes:
|> In article <1991Apr24.123035.4193@virtech.uucp>, cpcahil@virtech.uucp (Conor P. Cahill) writes:
|> > aed@netcom.COM (Andrew Davidson) writes:
|> > 
|> > >HOW BIG SHOULD MY SWAP BE? I have 8megs of ram
|> > 
|> > My general rule of thumb is 2x your memory (or 16mb for your system).  Of
|> > 
|> I've often wondered where the recommendation that 2 - 3x real memory should
|> be made available to swap comes from? Wouldn't this depend upon
|> whether or not the system is swapping at all? For instance, let's
|> say you have 48 meg of memory, and no swapping. Does this mean
|> I should tie up 100 - 150 meg of disk space for swap? Also, isn't
|> there less need for swap space with paging systems?

Nowadays when people talk about swapping, most of the time they really mean
paging. If I had to work with a machine that was swapping X-Servers and Clients,
I'd ask for twice may salary to make up for the mental abuse.

|> 
|> I would like to see some thoughts on the validity of these
|> rule-of-thumb recommendations. Not saying they are wrong, but would
|> like to know the justification behind them.
I'd say that the 2-3x ratio is from the old days when the average mini had 1MB
RAM and the disk to memory access ratio wan't quite as bad as it is now. Now if
it comes to the point where running processes steal pages from each others active
sets, you might as well switch it off. Today's rule of thumb is "it depends..."
It depends on the CPU, disk speed, main memory, number of users, types of
applications run, locality of reference, the day of the week and the mood of the
operator. I personally use 100-150% of what I have in main memory for swap space.
I don't make it less, because I want the system dumps to fit onto it. If the
paging is percetible, I add more RAM.
|> 
|> -- 
|> |---------------------------------------------------------------------|
|> |  Terry Linhardt      The Lafayette Group      uunet!jgaltstl!terry  | 
|> |---------------------------------------------------------------------|

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