Solaris ZFS Administration Guide

Installing and Booting a ZFS Root File System (Overview)

Starting in the SXCE, build 90 release, you can install and boot from a ZFS root file system in the following ways:

You can perform an initial installation where ZFS is selected as the root file system.
You can use the Solaris Live Upgrade feature to migrate a UFS root file system to a ZFS root file system. In addition, you can use Solaris Live Upgrade to perform the following tasks:
- Create a new boot environment within an existing ZFS root pool
- Create a new boot environment in a new ZFS root pool
You can use a Solaris JumpStart profile to automatically install a system with a ZFS root file system.
Systems that already have ZFS root file systems can be bfu'd to SXCE, build 90, but bfu does not convert the legacy mounts (of /, /var, and so on) to ZFS mounts. Backwards bfu to releases that don't support ZFS boot is prohibited.

We recommend that you reinstall your systems at some future time to achieve the standard ZFS boot configuration provided in this release, which uses ZFS mounts, not legacy mounts. However, the system continues to boot with legacy mounts, at least for now.

After a SPARC-based or an x86 based system is installed with a ZFS root file system or migrated to a ZFS root file system, the system boots automatically from the ZFS root file system. For more information about boot changes, see Booting From a ZFS Root File System.

ZFS Installation Features

The following ZFS installation features are provided in this Solaris release:

Using the Solaris interactive text installer, you can install a UFS or a ZFS root file system. The default file system is still UFS for this Solaris release. You can access the interactive text installer option in the following ways:
- On SPARC based system, use the following syntax from the Solaris installation DVD:
  ok boot cdrom - text
- On SPARC based system, use the following syntax when booting from the network:
  ok boot net - text
- On an x86 based system, select the text-mode install option when presented.
Custom JumpStart^TM features enable you to set up a profile to create a ZFS storage pool and designate a bootable ZFS file system.
Using the Solaris Live Upgrade feature, you can migrate a UFS root file system to a ZFS root file system. The lucreate and luactivate commands have been enhanced to support ZFS pools and file systems.
You can set up a mirrored ZFS root pool by selecting two disks during installation. Or, you can attach additional disks after installation to create a mirrored ZFS root pool.
Swap and dump devices are automatically created on ZFS volumes in the ZFS root pool.

The following installation features are not provided in this release:

The GUI installation feature for installing a ZFS root file system is not currently available.
The Solaris^TM Flash installation feature for installing a ZFS root file system is not currently available.
You cannot use the standard upgrade program to upgrade your UFS root file system to a ZFS root file system.

Solaris Installation and Solaris Live Upgrade Requirements for ZFS Support

Make sure the following requirements are met before attempting to install a system with a ZFS root file system or attempting to migrate a UFS root file system to a ZFS root file system.

Solaris Release Requirements

You can install and boot a ZFS root file system or migrate to a ZFS root file system in the following ways:

Install a ZFS root file system – Available starting in the SXCE, build 90 release.
Migrate from a UFS root file system to a ZFS root file system with Solaris Live Upgrade – You must have installed the SXCE, build 90 release or you must have upgraded to the SXCE, build 90 release. For a list of required Solaris Live Upgrade patches, see Required Solaris Live Upgrade Patch Information.

General ZFS Storage Pool Requirements

Review the following sections that describe ZFS root pool space and configuration requirements.

ZFS Storage Pool Space Requirements

The required minimum amount of available pool space for a ZFS root file system is larger than for a UFS root file system because swap and dump devices must be separate devices in a ZFS root environment. By default, swap and dump devices are the same device in a UFS root file system.

When a system is installed or upgraded with a ZFS root file system, the size of the swap area and the dump device are dependent upon the amount of physical memory. The minimum amount of available pool space for a bootable ZFS root file system depends upon the amount of physical memory, the disk space available, and the number of boot environments (BEs) to be created.

Review the following ZFS storage pool space requirements:

1 Gbyte of memory is recommended to install a ZFS root file system and for overall better ZFS performance
At least 16 Gbytes of disk space is recommended. The space is consumed as follows:
- Swap area and dump device – The default sizes of the swap and dump volumes that are created by the Solaris installation programs are as follows:
  - Solaris initial installation – The default swap volume size is calculated as half the size of physical memory, generally in the 512 Mbytes to 2 Gbytes range, in the new ZFS BE. You can adjust the swap size during an initial installation.
  - The default dump volume size is calculated by the kernel based on dumpadm information and the size of physical memory. You can adjust the dump size during an initial installation.
  - Solaris Live Upgrade – When a UFS root file system is migrated to a ZFS root file system, the default swap volume size for the ZFS boot environment (BE) is calculated as the size of the swap device of the UFS BE. The default swap volume size calculation simply adds the sizes of all the swap devices in the UFS BE, and creates a ZFS volume of that size in the ZFS BE. If no swap devices are defined in the UFS BE, then the default swap volume size is set to 512 Mbytes.
  - The default dump volume size is set to half the size of physical memory, between 512 Mbytes and 2 Gbytes, in the ZFS BE.
  You can adjust the sizes of your swap and dump volumes to sizes of your choosing as long as the new sizes support system operation. For more information, see Adjusting the Sizes of Your ZFS Swap and Dump Devices.
- Boot environment (BE) – In addition to either new swap and dump space requirements or adjusted swap and dump device sizes, a ZFS BE that is migrated from a UFS BE needs approximately 6 Gbytes. Each ZFS BE that is cloned from another ZFS BE doesn't need additional disk space, but consider that the BE size will increase when patches are applied. All ZFS BEs in the same root pool use the same swap and dump devices.
- Solaris OS Components – All subdirectories of the root file system that are part of the OS image, with the exception of /var, must be in the same dataset as the root file system. In addition, all Solaris OS components must reside in the root pool with the exception of the swap and dump devices.
For example, a system with 12 Gbytes of disk space might be too small for a bootable ZFS environment because 2 Gbytes of disk space is needed for each swap and dump device and approximately 6 Gbytes of disk space is needed for the ZFS BE that is migrated from a UFS BE.

ZFS Storage Pool Configuration Requirements

Review the following ZFS storage pool configuration requirements:

The pool that is intended for the root pool must have an SMI label. This requirement should be met if the pool is created with disk slices.
The pool must exist either on a disk slice or on disk slices that are mirrored. If you attempt to use an unsupported pool configuration during a Live Upgrade migration, you will see a message similar to the following:
ERROR: ZFS pool name does not support boot environments
For a detailed description of supported ZFS root pool configurations, see Creating a ZFS Root Pool.
On an x86 based system, the disk must contain a Solaris fdisk partition. A Solaris fdisk partition is created automatically when the x86 based system is installed. For more information about Solaris fdisk partitions, see Guidelines for Creating an fdisk Partition in System Administration Guide: Devices and File Systems.
Disks that are designated for booting in a ZFS root pool must be limited to 1 TB in size on both SPARC based and x86 based systems.
Compression can be enabled on the root pool but only after the root pool is installed. No way exists to enable compression on a root pool during installation. The gzip compression algorithm is not supported on root pools.
Do not rename the root pool after it is created by an initial installation or after Solaris Live Upgrade migration to a ZFS root file system. Renaming the root pool might cause an unbootable system.