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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Maybe but does Linux not do virtual memory
pool of both swap and physical memory? On UNIX such as HP-UX there is value
in having larger swap simply because it allows a larger preallocation of
virtual memory by processes thereby allowing more to be started at the same
time. This preallocation is for memory that is never really used for the most
part.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The key in the OP though was DB and that
is a little different. It doesn’t say what DB. I haven’t done
anything with MySQL but Oracle uses its own SGA which is in Shared Memory for
the most part. Swap really isn’t the issue for DB. Your DB ought to be
using space that isn’t using buffer cache either because it and the SGA’s
own caching mechanism interfere with each other. Since I’ve only done
Oracle on OCFS (Oracle Cluster Filesystem) or ASM raw devices I haven’t
investigated disabling buffer cache for ext3 or other filesystems. It is
something we routinely do for our Veritas filesystems on HP-UX.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
ale-bounces@ale.org [mailto:ale-bounces@ale.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Jim Kinney<br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, June 28, 2008 1:09
PM<br>
<b><span style='font-weight:bold'>To:</span></b> ale@ale.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [ale] Kernel 2.6 :
worst-case scenarios if swap full</span></font></p>
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12.0pt'> </span></font></p>
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face="Times New Roman"><span style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On Sat, Jun 28, 2008 at 10:42 AM, Ed L. Cashin <<a
href="mailto:ecashin@noserose.net">ecashin@noserose.net</a>> wrote:</span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>2008/6/28 Jim Kinney <<a href="mailto:jim.kinney@gmail.com">jim.kinney@gmail.com</a>>:<br>
...</span></font></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>> It's pretty easy to
add more swap space. Anthing over 2G is pretty useless<br>
> though.</span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I think there was a time when the kernel could not use more<br>
than 2 GB from a swap partition, but unless there has been<br>
a regression, I would expect today's kernels to use large swap<br>
areas without trouble.</span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
It is not a problem for the kernel to TB's of swap. It simply becomes useless
due to access speeds after about 2GB. </span></font></p>
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<blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;
margin-left:4.8pt;margin-right:0in'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br>
If there's a limit, though, I'd like to know about it. So any<br>
references where I could read about it would be appreciated.<br>
<font color="#888888"><span style='color:#888888'><br>
--<br>
Ed Cashin <<a href="mailto:ecashin@noserose.net">ecashin@noserose.net</a>></span></font></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>_______________________________________________<br>
Ale mailing list<br>
<a href="mailto:Ale@ale.org">Ale@ale.org</a><br>
<a href="http://mail.ale.org/mailman/listinfo/ale" target="_blank">http://mail.ale.org/mailman/listinfo/ale</a></span></font></p>
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</blockquote>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br clear=all>
<br>
-- <br>
-- <br>
James P. Kinney III </span></font></p>
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