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Old 04-30-2008, 10:58 AM   #1
Reginald0
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Swap size for a 16Gb RAM database/application server


Hi, folks!

I'm preparing a RHEL5 server with 16Gb RAM to be a database/application server (DB2/SAP) at our company, and I would like to know if there is an ideal size for swap partition for this kind of scenario.

Thanks in advance.

Reginald0
 
Old 04-30-2008, 11:29 AM   #2
Pikidalto
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With that amount of RAM, I don't really think a swap partition is necessary, unless you're going to load up almost as many programs as you've got RAM (in which case, a small swap of say, 128MB to 2GB would do, depending on how much memory you plan on using). If you plan on using suspend-to-disk/hibernate (which is NOT needed on a server since a server is generally always on), you'll need a swap partition large enough to hold all 16GB worth of RAM PLUS how much video card memory you have (again, generally not needed on a server).
 
Old 04-30-2008, 01:56 PM   #3
salasi
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Quote:
Originally Posted by Reginald0 View Post
I would like to know if there is an ideal size for swap partition for this kind of scenario.
Well, there is. Its just a shame we can't know what it is.

Even with this amount of RAM, I think I would always want some swap space so that if the worst happens and it does run out of ram, it slows down rather than does anything more abrupt. In that case, the fault is going to be easier to debug.

Depending on the databases, the working set of data could be quite large. this would influence the amount of ram that is optimal for the application. If, however, totalling up the programs and the working sets of data you come to a result that is quite clearly less than the amount of ram ('worst case' memory usage), you could quite happily decide on a small amount of ram, which in this context might be a couple of gig. If the worst case memory usage is pushing closer to the amount of ram (or even if it exceeds the amount of ram - and I don't even want to think about what you might be doing to cause this situation), you'd probably be better pushing the swap up a bit - say 8 G or more.

With the cost of disk space these days, if you are in any way uncertain, provision for too much rather than too little. You could even initially partition the system with a couple of different swap partition sizes and decide which to use finally based on testing (but, by the time you've created the swap partitions, you'd probably just leave them as swap, wouldn't you?).
 
  


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