System Administration Guide: Devices and File Systems

Allocating Swap Space for ZFS-Based Systems

During an initial installation of a ZFS root file system or a Solaris Live Upgrade from a UFS file system to a ZFS root file system, a swap area is automatically created on a ZFS volume in the ZFS root pool, generally in the 512 Mbyte to 2 Gbyte range. In the case of a UFS to ZFS migration by using Solaris Live Upgrade, a swap volume is created based on the sizes of existing swap areas.

In a ZFS root pool, swap devices are not pre-allocated to fixed-size slices, so it is fairly easy to modify the swap size later.

After you assess the swap requirements of your applications, you can use the default swap size or adjust the swap volume size during an initial installation or after the installation, if necessary.

During an initial installation, the default dump volume size is calculated by the kernel based on dumpadm information and the size of physical memory. During a Live Upgrade migration from a UFS root file system to a ZFS root file system, the default dump volume size is set to half the size of physical memory, between 512 Mbytes and 2 Gbytes, in the ZFS BE.

In a ZFS environment, file systems consume space from the pool so the /var/crash directory will consume what it needs depending on how many crash dumps are saved.

For more information about adjusting swap and dump sizes during or after installation in a ZFS environment, see this site: