Creating and Destroying ZFS Storage Pools

By design, creating and destroying pools is fast and easy. However, be cautious when doing these operations. Although checks are performed to prevent using devices known to be in use in a new pool, ZFS cannot always know when a device is already in use. Destroying a pool is even easier. Use zpool destroy with caution. This is a simple command with significant consequences. For information about destroy pools, see Destroying ZFS Storage Pools.

Creating a ZFS Storage Pool

To create a storage pool, use the zpool create command. This command takes a pool name and any number of virtual devices as arguments. The pool name must satisfy the naming conventions outlined in ZFS Component Naming Requirements.

Creating a Basic Storage Pool

The following command creates a new pool named tank that consists of the disks c1t0d0 and c1t1d0:

# zpool create tank c1t0d0 c1t1d0

These whole disks are found in the /dev/dsk directory and are labelled appropriately by ZFS to contain a single, large slice. Data is dynamically striped across both disks.

Creating a Mirrored Storage Pool

To create a mirrored pool, use the mirror keyword, followed by any number of storage devices that will comprise the mirror. Multiple mirrors can be specified by repeating the mirror keyword on the command line. The following command creates a pool with two, two-way mirrors:

# zpool create tank mirror c1d0 c2d0 mirror c3d0 c4d0

The second mirror keyword indicates that a new top-level virtual device is being specified. Data is dynamically striped across both mirrors, with data being replicated between each disk appropriately.

Creating a RAID-Z Storage Pool

Creating a RAID-Z pool is identical to creating a mirrored pool, except that the raidz keyword is used instead of mirror. The following example shows how to create a pool with a single RAID-Z device that consists of five disks:

# zpool create tank raidz c1t0d0 c2t0d0 c3t0d0 c4t0d0 /dev/dsk/c5t0d0

This example demonstrates that disks can be specified by using their full paths. The /dev/dsk/c5t0d0 device is identical to the c5t0d0 device.

A similar configuration could be created with disk slices. For example:

# zpool create tank raidz c1t0d0s0 c2t0d0s0 c3t0d0s0 c4t0d0s0 c5t0d0s0

However, the disks must be preformatted to have an appropriately sized slice zero.

For more information about a RAID-Z configuration, see RAID-Z Storage Pool Configuration.

Handling ZFS Storage Pool Creation Errors

Pool creation errors can occur for many reasons. Some of these reasons are obvious, such as when a specified device doesn't exist, while other reasons are more subtle.

Detecting in Use Devices

Before formatting a device, ZFS first determines if the disk is in use by ZFS or some other part of the operating system. If the disk is in use, you might see errors such as the following:

# zpool create tank c1t0d0 c1t1d0
invalid vdev specification
use '-f' to override the following errors:
/dev/dsk/c1t0d0s0 is currently mounted on /
/dev/dsk/c1t0d0s1 is currently mounted on swap
/dev/dsk/c1t1d0s0 is part of active ZFS pool 'zeepool'
Please see zpool(1M)

Some of these errors can be overridden by using the f option, but most errors cannot. The following uses cannot be overridden by using the f option, and you must manually correct them:

Mounted file system

The disk or one of its slices contains a file system that is currently mounted. To correct this error, use the umount command.

File system in /etc/vfstab

The disk contains a file system that is listed in the /etc/vfstab file, but the file system is not currently mounted. To correct this error, remove or comment out the line in the /etc/vfstab file.

Dedicated dump device

The disk is in use as the dedicated dump device for the system. To correct this error, use the dumpadm command.

Part of a ZFS pool

The disk or file is part of an active ZFS storage pool. To correct this error, use the zpool command to destroy the pool.

The following in-use checks serve as helpful warnings and can be overridden by using the f option to create the pool:

Contains a file system

The disk contains a known file system, though it is not mounted and doesn't appear to be in use.

Part of volume

The disk is part of an SVM volume.

Live upgrade

The disk is in use as an alternate boot environment for Solaris Live Upgrade.

Part of exported ZFS pool

The disk is part of a storage pool that has been exported or manually removed from a system. In the latter case, the pool is reported as potentially active, as the disk might or might not be a network-attached drive in use by another system. Be cautious when overriding a potentially active pool.

The following example demonstrates how the f option is used:

# zpool create tank c1t0d0
invalid vdev specification
use '-f' to override the following errors:
/dev/dsk/c1t0d0s0 contains a ufs filesystem
# zpool create -f tank c1t0d0

Ideally, correct the errors rather than use the f option.

Mismatched Replication Levels

Creating pools with virtual devices of different replication levels is not recommended. The zpool command tries to prevent you from accidentally creating a pool with mismatched replication levels. If you try to create a pool with such a configuration, you see errors similar to the following:

# zpool create tank c1t0d0 mirror c2t0d0 c3t0d0
invalid vdev specification
use '-f' to override the following errors:
mismatched replication level: both disk and mirror vdevs are present
# zpool create tank mirror c1t0d0 c2t0d0 mirror c3t0d0 c4t0d0 c5t0d0
invalid vdev specification
use '-f' to override the following errors:
mismatched replication level: 2-way mirror and 3-way mirror vdevs are present

You can override these errors with the f option, though this practice is not recommended. The command also warns you about creating a mirrored or RAID-Z pool using devices of different sizes. While this configuration is allowed, mismatched replication levels result in unused space on the larger device, and requires the f option to override the warning.

Doing a Dry Run of Storage Pool Creation

Because creating a pool can fail unexpectedly in different ways, and because formatting disks is such a potentially harmful action, the zfs create command has an additional option, n, which simulates creating the pool without actually writing data to disk. This option performs the device in-use checking and replication level validation, and reports any errors in the process. If no errors are found, you see output similar to the following:

# zpool create -n tank mirror c1t0d0 c1t1d0
would create 'tank' with the following layout:


Some errors cannot be detected without actually creating the pool. The most common example is specifying the same device twice in the same configuration. This error cannot be reliably detected without writing the data itself, so the create -n command can report success and yet fail to create the pool when run for real.

Default Mount Point for Storage Pools

When a pool is created, the default mount point for the root dataset is /pool-name by default. This directory must either not exist or be empty. If the directory does not exist, it is automatically created. If the directory is empty, the root dataset is mounted on top of the existing directory. To create a pool with a different default mount point, use the m option of the zpool create command:

# zpool create home c1t0d0
default mountpoint '/home' exists and is not empty
use '-m' option to specify a different default
# zpool create -m /export/zfs home c1t0d0

This command creates a new pool home and the home dataset with a mount point of /export/zfs.

For more information about mount points, see Managing ZFS Mount Points.

Destroying ZFS Storage Pools

Pools are destroyed by using the zpool destroy command. This command destroys the pool even if it contains mounted datasets.

# zpool destroy tank


Be very careful when you destroy a pool. Make sure you are destroying the right pool and you always have copies of your data. If you accidentally destroy the wrong pool, you can attempt to recover the pool. For more information, see Recovering Destroyed ZFS Storage Pools.

Destroying a Pool With Faulted Devices

The act of destroying a pool requires that data be written to disk to indicate that the pool is no longer valid. This state information prevents the devices from showing up as a potential pool when you perform an import. If one or more devices are unavailable, the pool can still be destroyed. However, the necessary state information won't be written to these damaged devices.

These devices, when suitably repaired, are reported as potentially active when you create a new pool, and appear as valid devices when you search for pools to import. If a pool has enough faulted devices such that the pool itself is faulted (meaning that a top-level virtual device is faulted), then the command prints a warning and cannot complete without the f option. This option is necessary because the pool cannot be opened, so whether data is stored there or not is unknown. For example:

# zpool destroy tank
cannot destroy 'tank': pool is faulted
use '-f' to force destruction anyway
# zpool destroy -f tank

For more information about pool and device health, see Health Status of ZFS Storage Pools.

For more information about importing pools, see Importing ZFS Storage Pools.