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You take one of a couple of alternatives, because you seem to love swap, for some reason, which is a legacy leftover from the days of expensive memory; and then you try to justify your position by insisting to dump in swap.
I don't think I ever wrote or suggested I loved swap. Swap isn't something to be loved or hated but something that need not be undersized.
To properly size the swap area, there are two factors to take into account.
1: at the peak virtual memory consumption, all memory reservations need to be backed by either RAM or swap area pages. This doesn't means any activity will necessarily occur on the swap, just the pages have to be there. Solaris isn't doing lazy memory allocation like the Linux kernel does. The free virtual memory can be easily monitored and it is easy to increase its size by adding new swap devices or swap files, so this first point isn't that much of a problem.
2: The default Solaris configuration is to have crash dumps to be written on the swap. Many (but not 99.9% of) Solaris installations are using this standard configuration. In the old Solaris 2.x days, the swap area was very often larger than the RAM size because the (already obsolete) rule of thumb x2 was still followed. There was no risk for the crash dump not to fit. Nowadays, it is not uncommon to have the RAM much larger than the swap. That means there is a risk to miss the invaluable data stored there should a panic happen. I'm not telling this risk cannot be overcome, I'm telling many people are unaware of this risk because it is not common to monitor the kernel size and even less common to check if it would fit in the dump device should a panic occur.
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Believe me. You do not need swap in most modern systems. Swap slows you down - why do it with memory is cheap.
Swap doesn't slows you down, lack of RAM slows you down when swap is available and crashes your application when no swap is there. I strongly prefer my applications to slow down and the OS to paginate than seeing random applications crashing because of malloc failures.
There are also usage profiles were using disk instead of RAM to store virtual memory make sense. If a process, say a whole SunRAY user session, isn't going to be used for days, what is the point keeping its data bits on RAM ? Better to use that RAM as file cache for live applications.
RAM is cheap, true, but disks are definitely cheaper.
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You don't need to dump in swap either.
Indeed but the issue is most people do it because it's the default.
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reborg's orginal statement on this was not misleading.
Perhaps did I pick the wrong word. I don't say the statement is incorrect, I just say that statement would deserve some explanations. I have met several unexperienced Solaris administrators who wrongly thought the crash dump was directly written to the savecore directory. On the other hand, I'm glad Reborg enlighten us about the undocumented way to save the dumps on an UFS file.