Are these real or virtual systems? Memory management in a virtual machine may be strange and is certainly specific to the type of virtualization.
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Originally Posted by kopper27
they set an alarm for swap memory to 10%(critical) I really has no idea when swap memory usage is high....
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You mean 10% swap used and 90% swap free, not the other way around, correct?
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Can someone recommend me a threshold for this? when is warning or critical and this parameters can affect performance in my Suse Linux boxes?
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Without knowing a lot more, we can't say what % would be a problem. For a workstation or small server I think 2GB of free swap is an appropriate margin. For a larger server, you should have a little more than that.
How much swap space and how much ram do these systems have? That info would give a little perspective on the % values you reported.
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for instance 1 box has been having "peaks" of 14% during last days....
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If you have 2GB of swap and 14% is used, you probably should fix something. If you have 4GB of swap and 14% is used, there is less likely any need to correct anything.
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today another box had a peak of 64% and they are worried should they?
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64% swap use sounds like a problem. If your system had unusually high swap usage for a well understood reason and someone had set the swap size to a safe margin above that, it could have 64% swap usage and be perfectly correct and safe. But that doesn't sound like your situation. Either the swap allocation is low so a reasonable use of swap space fills 64% (meaning you ought to have much more swap allocation) or you have an unexpected large use of swap space that you should examine.
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they told me these 2 boxes should not have peaks like that they should be 0% swap usage....so how they say that
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0% swap usage is a foolish target. Servers should use some swap space. But servers should also have a generous margin of free swap space.
If you can run free at a moment when swap usage is "high", you can get a better idea of the overall memory state.
If the used swap reported by
free is lower than cached ram reported by
free, you have moderate to low swap usage. Under those conditions, I think 2GB of free swap space is a pretty safe margin.
If the used swap is greater than the cached ram, you should be worrying about both the swap in/out rates for whether the system has enough ram to do its job and the out of memory killer (whether the system has enough swap space for safe operation). In such a system, I do not think 2GB of free swap is enough of a safety margin.