Requirements for Installing a ZFS Root Pool

Table 6-1 System Requirements and Limitations

Requirement or Limitation	Description	Information
Memory	768 MB is the minimum memory. 1 GB is recommended for overall performance.	ZFS Administration Guide.
Disk space	The minimum amount of available pool space for a bootable ZFS root file system depends on the amount of physical memory, the disk space available, and the number of boot environments to be created.	For an explanation, see Disk Space Requirements for a ZFS Installation.
The ZFS storage pool must be created with slices rather than whole disks to be upgradeable and bootable.	The pool created with slices can be mirrored but not a RAID-Z or non-redundant configuration of multiple disks. The SVM device information must be already available in the `/dev/md/[r]dsk` directory. The pool must have an SMI label. An EFI-labeled disk cannot be booted. x86 only: The ZFS pool must be in a slice with an `fdisk` partition.	For information about SVM, see Overview of Solaris Volume Manager Components. For information about other restrictions for an EFI-labled disk, see Overview of Disk Management in System Administration Guide: Devices and File Systems. To create an `fdisk` partition with an SMI label, see How to Create a Solaris fdisk Partition in System Administration Guide: Devices and File Systems. For information about `fdisk` partitions, see x86: Partitioning Recommendations.
When you migrate from a UFS root (`/`) file system to a ZFS root pool with Solaris Live Upgrade, consider these requirements.	Migrating from a UFS file system to a ZFS root pool with Solaris Live Upgrade or creating a new boot environment in a root pool is new starting with the Solaris 10 10/08 release. This release contains the software needed to use Solaris Live Upgrade with ZFS. You must have at least this release installed to use ZFS with Solaris Live Upgrade. Migration is possible only from a UFS file system to a ZFS file system. File systems other than a UFS file system cannot be migrated to a ZFS root pool. A UFS file system cannot be created from a ZFS root pool. Before migrating, a ZFS storage pool must exist.	For more limitations on using Solaris Live Upgrade, see System Requirements and Limitations When Using Solaris Live Upgrade in Oracle Solaris 10 9/10 Installation Guide: Solaris Live Upgrade and Upgrade Planning. For step-by-step procedures, see Migrating a UFS File System to a ZFS File System in Oracle Solaris 10 9/10 Installation Guide: Solaris Live Upgrade and Upgrade Planning.

Disk Space Requirements for a ZFS Installation

Normally, on a system with a UFS root file system, swap and dump are on the same slice. Therefore, UFS shares the swap space with the dump device. In a ZFS root pool, swap and dump are separate zvols, so they do not share the same physical space. 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 on the amount of physical memory. The minimum amount of available pool space for a bootable ZFS root file system depends on the amount of physical memory, the disk space available, and the number of boot environments to be created. Approximately 1 Gbyte of memory and at least 2 Gbytes of disk space are recommended. The space is consumed as follows:

Swap area and dump device - The default size of swap is 1/2 the size of physical memory, but no less than 512 Mbytes and no greater than 2 Gbytes. The dump device is calculated based on the size of the memory and the contents of the dumpadm.conf file. This file defines what goes into a crash dump. You can adjust the sizes of your swap and device volumes before or after installation. For more information, see Introducing ZFS Properties in Oracle Solaris ZFS Administration Guide.
Boot environments - In addition to either new swap and dump space requirements or adjusted swap and dump device sizes, a ZFS boot environment that is migrated from a UFS boot environment needs approximately 6 Gbytes. Each ZFS boot environment that is cloned from another ZFS boot environment does not need additional disk space. However, the boot environment size might increase when patches are applied. All ZFS boot environments in the same root pool use the same swap and dump devices.

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