CentOS - Jul 2009 - what would be happen if swap partition is not?

Hello, all.

 

I know the function of the swap and can make swap partion or file. 

 

But, if there is no swap partion at system, what would be happen?

that makes the system unstable or not?

 

I have one system that has no swap, but there was no problem until now.

 

 

Thanks in advance.

 

_________________________________________________________________
???? ????! ??? ??? ???? ????! ??? ??! 25GB ???? ?! ???? ??? ?? ??
http://im.msn.co.kr/Univ/
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2009/7/3 MontyRee <chulmin2 at hotmail.com>
>  Hello, all.
>
> I know the function of the swap and can make swap partion or file.
>
> But, if there is no swap partion at system, what would be happen?
> that makes the system unstable or not?
>
> I have one system that has no swap, but there was no problem until now.
>
>
> Thanks in advance.
>
>
> ------------------------------
>
The swap file is there to provide extra memory when the physical RAM runs
out. But if you have a lot (say 4GB+) ram in your machine, you may not
even necessarily use swap. So, getting back to your question, it wont' cause
problems - unless you run programs which consume more resources than the
physical RAM in the PC.



-- 
Kind Regards
Rudi Ahlers
CEO, SoftDux Hosting
Web: http://www.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532
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At Fri, 3 Jul 2009 12:46:34 +0000 CentOS mailing list <centos at
centos.org> wrote:
> 
> 
> 
> 
> Hello, all.
> 
>  
> 
> I know the function of the swap and can make swap partion or file. 
> 
>  
> 
> But, if there is no swap partion at system, what would be happen?
> 
> that makes the system unstable or not?
> 
>  
> 
> I have one system that has no swap, but there was no problem until now.
A swap partition is not essential to system operation so long as you
have enough RAM.  Most modern systems have more then enough RAM and can
probably live without a swap partition .
> 
>  
> 
>  
> 
> Thanks in advance.
> 
>  
> 
> _________________________________________________________________
> ???????????????? ????????????! )???????? ?????????? ??????????????
??????????????! ??????: ?????! 25GB ??????????: ????! ????????????????
?????????? )???? ??????
> http://im.msn.co.kr/Univ/
> MIME-Version: 1.0
> 
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
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2009/7/3 MontyRee <chulmin2 at hotmail.com>
>  Hello, all.
>
> I know the function of the swap and can make swap partion or file.
>
> But, if there is no swap partion at system, what would be happen?
> that makes the system unstable or not?
>
> I have one system that has no swap, but there was no problem until now.
>
Hate giving this answer, but "it depends."

You *can* run a system without page space, but you should really know what
you're doing before you do this. It can work for types of workloads, but can
get you into trouble in many situations.

If you do run without page space, you should configure the kernel overcommit
options. You should also configure your application ulimits so that they
behave more predictably in case they cannot allocate memory. You should also
verify that your applications can properly handle a failed memory request.

To your question:  For a well-known application, running without page space
can make it more reliable *if* (and a big IF) all other applications are
predictable.  For example, say you're running you're well behaved
application... Another process suddenly starts consuming memory. Your
application then tries to allocate some memory. It cannot, so it crashes.

There are a ton of threads about how large the page space should be, given
modern multi-gigabyte RAM spaces. There are threads about whether a page
file or page volume is better.  What's best will depend entirely on your
workload and requirements :)

As your post demonstrates, a page-less system can run fine. The bigger your
RAM space, the less likely you are to run into issues.
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On 07/03/2009 05:46 AM, MontyRee wrote:
>
> But, if there is no swap partion at system, what would be happen?
> that makes the system unstable or not?
That depends on what you're running.  As people point out, you can 
usually get along without one, but doing so is a bad idea in some 
configurations.  If you run a server that's dedicated to any single 
large application (like dedicated tomcat or database server), then you 
should have swap at least as large as RAM.  Even when you configure the 
system so that applications stay within the bounds of RAM, fork() will 
fail in your application if it doesn't have room for a complete second 
copy of itself in memory.  The space won't normally be used, since Linux 
uses a copy-on-write technique for fork(), but it still requires the 
space before it will allow fork() to succeed.