Swap Question

Swap Question

[Steve Holmes]

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Hey, the swap question has come up for me now as I will probably be
rebuilding my Linux environment.  The old days with small memory, it
was recommended to have a swap something like twice the system
memory.  But with larger systems, that seems less valid as I've been
hearing.  I have 2 GB of main system memory and when I include the
high-memory option in the kernel, I get all of it available to me.
With 2 gigs, would it be necessary to have any swap at all? I mean,
with this big a machine, could I go and install Linux and not have a
swap at all? I will probably be doing Slackware again do to my
familiarity with it.  When I looked briefly at Debian the other day,
it appeared to me that the installer would insist on building a swap
partition regardless of my memory size.

I'm just wondering if anyone has some ideas on this topic.  Thanks.
- -- 
HolmesGrown Solutions
The best solutions for the best price!
http://holmesgrown.ld.net/
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Re: Swap Question

[Kerry Hoath]

You can do without swap if you must; however allocating a few hundred megs 
of swap on a multi-gigabyte drive won't hurt and can in fact improve things 
in a number of ways:
1: If a process is idle and taking up a large amount of memory; it can be 
swapped out to disk to allow other processes to use the
memory. Think virtualization, web servers and the like.
without swap; when the kernel runs out of memory it will start killing 
processes; this can get ugly.
With swap; you notice the system is using swap and can do something about it 
before things go critical.
secondly: tuxonice and uswsusp 2 of the hybernate solutions for Linux write 
the suspend images to the swap space.
If you don't have swap then you can't suspend to disk.
s2both suspends to disk and ram; so if you power up the machine again from 
standby the memory image is used; if that fails the disk snapshot is used.

my personal recommendation is to allocate the maximum your physical ram is 
likely to be to swapspace, in your current case; 2gb of swap.

With large capacity drives beeing under 30 cents a gig; this is not really a 
problem in 2007.

swap partitions are faster to access; however if you allocate space to swap 
then get more ram you can allways add in a swap file. In fact; there are 
howto documents on how to share swapspace between Windows and Linux if that 
helps also.
Regards, Kerry.

----- Original Message ----- 
From: "Steve Holmes" <steve@holmesgrown.com>
To: <speakup@braille.uwo.ca>
Sent: Monday, January 07, 2008 5:44 PM
Subject: Swap Question


> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: RIPEMD160
>
> Hey, the swap question has come up for me now as I will probably be
> rebuilding my Linux environment.  The old days with small memory, it
> was recommended to have a swap something like twice the system
> memory.  But with larger systems, that seems less valid as I've been
> hearing.  I have 2 GB of main system memory and when I include the
> high-memory option in the kernel, I get all of it available to me.
> With 2 gigs, would it be necessary to have any swap at all? I mean,
> with this big a machine, could I go and install Linux and not have a
> swap at all? I will probably be doing Slackware again do to my
> familiarity with it.  When I looked briefly at Debian the other day,
> it appeared to me that the installer would insist on building a swap
> partition regardless of my memory size.
>
> I'm just wondering if anyone has some ideas on this topic.  Thanks.
> - -- 
> HolmesGrown Solutions
> The best solutions for the best price!
> http://holmesgrown.ld.net/
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.7 (GNU/Linux)
>
> iD8DBQFHgeaIWSjv55S0LfERA0fDAJ9/LmLZ+G2OOyAqzbGSubo/YbctXwCgq2gB
> Yv42oBYY+42Lc1dcQZ2na9E=
> =jErU
> -----END PGP SIGNATURE-----
>
> _______________________________________________
> Speakup mailing list
> Speakup@braille.uwo.ca
> http://speech.braille.uwo.ca/mailman/listinfo/speakup
> 

Re: Swap Question

[Joseph C. Lininger]

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Hello Steve,
I realize that machines are coming with larger amounts of RAM. The thing
is, applications require more now than they used to. This isn't as true
of console apps as it is of GUI applications, but it is true to an
extent. Also, if you want to use a hibernation solution of some sort,
(machine saves memory to disk and then shuts down) you will need at
least a swap space equal to that of your ram. I personally still
allocate double my RAM size, at least on machines having a gb or less. I
also do it on machines that are likely to use a lot of memory, like
machines with GUI components or server systems. It doesn't hurt anything
with the cost of disk space being so low. At a minimum, you should make
a swap partition or swap file that is at least equal to the size of your
RAM.

Steve Holmes wrote:
> Hey, the swap question has come up for me now as I will probably be
> rebuilding my Linux environment.  The old days with small memory, it
> was recommended to have a swap something like twice the system
> memory.  But with larger systems, that seems less valid as I've been
> hearing.  I have 2 GB of main system memory and when I include the
> high-memory option in the kernel, I get all of it available to me.
> With 2 gigs, would it be necessary to have any swap at all? I mean,
> with this big a machine, could I go and install Linux and not have a
> swap at all? I will probably be doing Slackware again do to my
> familiarity with it.  When I looked briefly at Debian the other day,
> it appeared to me that the installer would insist on building a swap
> partition regardless of my memory size.
> 
> I'm just wondering if anyone has some ideas on this topic.  Thanks.

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Re: Swap Question

[Ralph W. Reid]

Depending on what you do with the system, there is still a chance that
some swapping might occur (a very slim chance at this point in time
perhaps).  On my big system (8 GB of RAM) I have a swap partition of 2
GB to catch any overflow--although I have no idea what I will do in
the near future which will actually use it.  If the `free' command
shows that I ever access swap memory, I will definitely be doing
something big.  If you do not expect to need any swapping but later
find that you do, you can always set up a swap file on an existing
partition to handle the situation, and then perhaps add another hard
drive for a more permanent swap partition if needed.  In any case,
setting up a swap partition as large as twice your system memory (4
GB) seems kind of large--how slow your system will be if you actually
start swapping several GB at a time...  How much swap space to
allocate has been debated for many years, and the decision comes down
to a slightly educated guess and your own judgement.

HTH, and have a great day.

On Mon, Jan 07, 2008 at 01:44:56AM -0700, Steve Holmes wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: RIPEMD160
> 
> Hey, the swap question has come up for me now as I will probably be
> rebuilding my Linux environment.  The old days with small memory, it
> was recommended to have a swap something like twice the system
> memory.  But with larger systems, that seems less valid as I've been
> hearing.  I have 2 GB of main system memory and when I include the
> high-memory option in the kernel, I get all of it available to me.
> With 2 gigs, would it be necessary to have any swap at all? I mean,
> with this big a machine, could I go and install Linux and not have a
> swap at all? I will probably be doing Slackware again do to my
> familiarity with it.  When I looked briefly at Debian the other day,
> it appeared to me that the installer would insist on building a swap
> partition regardless of my memory size.
> 
> I'm just wondering if anyone has some ideas on this topic.  Thanks.
> - -- 
> HolmesGrown Solutions
> The best solutions for the best price!
> http://holmesgrown.ld.net/
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> Version: GnuPG v1.4.7 (GNU/Linux)
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> iD8DBQFHgeaIWSjv55S0LfERA0fDAJ9/LmLZ+G2OOyAqzbGSubo/YbctXwCgq2gB
> Yv42oBYY+42Lc1dcQZ2na9E=
> =jErU
> -----END PGP SIGNATURE-----

-- 
Ralph.  N6BNO.  Wisdom comes from central processing, not from I/O.
rreid@sunset.net  http://personalweb.sunset.net/~rreid
...passing through The City of Internet at the speed of light...
SECANT (x) = TAN (x) / COTAN (x)