Planning for Swap Space

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The most important factors in determining swap space size are the requirements of the system's software applications. For example, large applications such as computer-aided design simulators, database management products, transaction monitors, and geologic analysis systems can consume as much as 200–1000 MB of swap space.

Consult your application vendors for swap space requirements for their applications.

If you are unable to determine swap space requirements from your application vendors, use the following general guidelines based on your system type to allocate swap space.

Note - Crash dump content is compressed so the dump device does not have to be the same size as physical memory. By default, the dump content value is set to kernel pages. However, if the dump content value is set to dump all memory pages, then consider increasing the dump size to half the size of physical memory or more.

Table 3-1 Swap and Dump Volume Sizes for ZFS File Systems

System Type	Swap Volume Size	Dump Volume Size
System with about 4 GB of physical memory	1 GB	2 GB
Mid-range server with about 8 GB of physical memory	2 GB	4 GB
High-end server with about 16 to 128 GB of physical memory	4 GB	8-64 GB
High-end server with more than 128 GB of physical memory	1/4 of physical memory size	1/2 of physical memory size

Note - A busy system with many active ZFS file systems might use 1/2 to 3/4 the size of physical memory for the size of the dump device.

On a system with a ZFS root file system, if you attempt to designate a dump device that is too small to hold a system crash system with the dumpadm –d command, you will see a message similar to the following:

dumpadm: dump device /dev/zvol/dsk/rpool/dump is too small to hold a
system dump dump size 43467329536 bytes, device size 42949672960 bytes