"How do I add extra ZFS swap in Solaris 11.3?"

Post #303028648 by jlliagre on Friday 11th of January 2019 09:36:15 PM

Old 1 Week Ago
Originally Posted by feroccimx
The 3 TB swap comes from a recommendation to have 1.5 times RAM. This gave relief to our system which experienced severe performance issues.
Were they performance issues (like thrashing) or reliability issues (like coredumps)?

In general, increasing the swap area size is not expected to significantly improve performance (although in your case, the swap area is very undersized), but it can prevent programs to crash or to fail to start.

According to the statistics you wrote on the first post, there is 1.7T of virtual memory on your system with a tiny 4G being backed by your existing swap area.

The system is using 240 G of this virtual memory, two third of which being only reserved. You need at least 150 G of swap not to waste RAM (reserved size).

The actual swap size requirement depends on what precisely is running on your machine and each application way to use memory, but also about your dumpadm configuration. In case of a kernel panic, you might want to save the crashdump for further analysis and then a large swap area, like between 1/4 to 3/4 of the RAM size would make sense.

In any case, as long as the file systems also have enough free space, too large a swap doesn't hurt performance. There is a common misconception that a large swap will induce pagination. It doesn't make sense. What triggers pagination is RAM shortage, not swap availability.
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jim mcnamara (1 Week Ago)