Evaluating the Current System Setup

Zones can be used on any machine that runs the Solaris 10 release. The following primary machine considerations are associated with the use of zones.

• The performance requirements of the applications running within each zone.

• The availability of disk space to hold the files that are unique within each zone.

Disk Space Requirements

There are no limits on how much disk space can be consumed by a zone. The global administrator is responsible for space restriction. The global administrator must ensure that local storage is sufficient to hold a non-global zone's root file system. Even a small uniprocessor system can support a number of zones running simultaneously.

The nature of the packages installed in the global zone affects the space requirements of the non-global zones that are created. The number of packages and space requirements are factors.

Sparse Root Zones

In the Solaris 10 release, non-global zones that have inherit-pkg-dir resources are called sparse root zones.

The sparse root zone model optimizes the sharing of objects in the following ways:

• Only a subset of the packages installed in the global zone are installed directly into the non-global zone.

• Read-only loopback file systems, identified as inherit-pkg-dir resources, are used to gain access to other files.

In this model, all packages appear to be installed in the non-global zone. Packages that do not deliver content into read-only loopback mount file systems are fully installed. There is no need to install content delivered into read-only loopback mounted file systems since that content is inherited (and visible) from the global zone.

• As a general guideline, a zone requires about 100 megabytes of free disk space per zone when the global zone has been installed with all of the standard Solaris packages.

• By default, any additional packages installed in the global zone also populate the non-global zones. The amount of disk space required might be increased accordingly, depending on whether the additional packages deliver files that reside in the inherit-pkg-dir resource space.

An additional 40 megabytes of RAM per zone are suggested, but not required on a machine with sufficient swap space.

Whole Root Zones

The whole root zone model provides the maximum configurability. All of the required and any selected optional Solaris packages are installed into the private file systems of the zone. The advantages of this model include the capability for global administrators to customize their zones file system layout. This would be done, for example, to add arbitrary unbundled or third-party packages.

The disk requirements for this model are determined by the disk space used by the packages currently installed in the global zone.

Restricting Zone Size

The following options can be used to restrict zone size:

• You can place the zone on a lofi-mounted partition. This action will limit the amount of space consumed by the zone to that of the file used by lofi. For more information, see the lofiadm(1M) and lofi(7D) man pages.

• You can use soft partitions to divide disk slices or logical volumes into partitions. You can use these partitions as zone roots, and thus limit per-zone disk consumption. The soft partition limit is 8192 partitions. For more information, see Chapter 12, Soft Partitions (Overview), in Solaris Volume Manager Administration Guide.

• You can use the standard partitions of a disk for zone roots, and thus limit per-zone disk consumption.