Creating a ZFS Storage Pool (Solaris ZFS Administration Guide)

Solaris ZFS Administration Guide

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 redundant between each disk appropriately.

For more information about recommended mirrored configurations, see the following site:

http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide

Currently, the following operations are supported on a ZFS mirrored configuration:

Adding another set of disks for an additional top-level vdev to an existing mirrored configuration. For more information, see Adding Devices to a Storage Pool.
Attaching additional disks to an existing mirrored configuration. Or, attaching additional disks to a non-replicated configuration to create a mirrored configuration. For more information, see Attaching and Detaching Devices in a Storage Pool.
Replacing a disk or disks in an existing mirrored configuration as long as the replacement disks are greater than or equal to the device to be replaced. For more information, see Replacing Devices in a Storage Pool.
Detaching a disk in a mirrored configuration as long as the remaining devices provide adequate redundancy for the configuration. For more information, see Attaching and Detaching Devices in a Storage Pool.

Currently, the following operations are not supported on a mirrored configuration:

You cannot outright remove a top-level device from a mirrored storage pool. An RFE is filed for this feature.

Creating a ZFS Root Pool

In current Solaris releases, you can install and boot from a ZFS root file system. Review the following root pool configuration information:

Disks used for the root pool must have a VTOC (SMI) label and the pool must be created with disk slices
A root pool must be created as a mirrored configuration or a single-disk configuration. You cannot add additional disks to create multiple mirrored top-level virtual devicess by using the zpool add command, but you can expand a mirrored virtual device by using the zpool attach command.
A RAID-Z or a striped configuration is not supported
A root pool cannot have a separate log device

If you attempt to use an unsupported configuration for a root pool, you will see messages similar to the following:

ERROR: ZFS pool <pool-name> does not support boot environments

# zpool add -f rpool log c0t6d0s0
cannot add to 'rpool': root pool can not have multiple vdevs or separate logs

For more information about installing and booting a ZFS root file system, see Chapter 5, Installing and Booting a ZFS Root File System.

Creating RAID-Z Storage Pools

Creating a single-parity RAID-Z pool is identical to creating a mirrored pool, except that the raidz or raidz1 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 illustrates that disks can be specified by using their full paths, if desired. 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.

You can create a double-parity RAID-Z configuration by using the raidz2 keyword when the pool is created. For example:

You can create a double-parity or triple-parity RAID-Z configuration by using the raidz2 or raidz3 keyword when the pool is created. For example:

# zpool create tank raidz2 c1t0d0 c2t0d0 c3t0d0
# zpool status -v tank
  pool: tank
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz2-0  ONLINE       0     0     0
            c1t0d0  ONLINE       0     0     0
            c2t0d0  ONLINE       0     0     0
            c3t0d0  ONLINE       0     0     0

errors: No known data errors

# zpool create tank raidz3 c1t0d0 c2t0d0 c3t0d0 c4t0d0 c5t0d0
# zpool status -v tank
  pool: tank
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz3-0  ONLINE       0     0     0
            c1t0d0  ONLINE       0     0     0
            c2t0d0  ONLINE       0     0     0
            c3t0d0  ONLINE       0     0     0
            c4t0d0  ONLINE       0     0     0
            c5t0d0  ONLINE       0     0     0

errors: No known data errors

Currently, the following operations are supported on a ZFS RAID-Z configuration:

Add another set of disks for an additional top-level vdev to an existing RAID-Z configuration. For more information, see Adding Devices to a Storage Pool.
Replace a disk or disks in an existing RAID-Z configuration as long as the replacement disks are greater than or equal to the device to be replaced. For more information, see Replacing Devices in a Storage Pool.

Currently, the following operations are not supported on a RAID-Z configuration:

Attach an additional disk to an existing RAID-Z configuration.
Detach a disk from a RAID-Z configuration.
You cannot outright remove a device from a RAID-Z configuration. An RFE is filed for this feature.

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

Creating a ZFS Storage Pool with Log Devices

By default, the ZIL is allocated from blocks within the main pool. However, better performance might be possible by using separate intent log devices, such as NVRAM or a dedicated disk. For more information about ZFS log devices, see Setting Up Separate ZFS Logging Devices.

You can set up a ZFS logging device when the storage pool is created or after the pool is created.

For example, create a mirrored storage pool with mirrored log devices.

# zpool create datap mirror c1t1d0 c1t2d0 mirror c1t3d0 c1t4d0 log mirror c1t5d0 c1t8d0
# zpool status datap
  pool: datap
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        datap       ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            c1t1d0  ONLINE       0     0     0
            c1t2d0  ONLINE       0     0     0
          mirror-1  ONLINE       0     0     0
            c1t3d0  ONLINE       0     0     0
            c1t4d0  ONLINE       0     0     0
        logs
          mirror-2  ONLINE       0     0     0
            c1t5d0  ONLINE       0     0     0
            c1t8d0  ONLINE       0     0     0

errors: No known data errors

For information about recovering from a log device failure, see Example 11–2.

Creating a ZFS Storage Pool with Cache Devices

You can create a storage pool with cache devices to cache storage pool data. For example:

# zpool create tank mirror c2t0d0 c2t1d0 c2t3d0 cache c2t5d0 c2t8d0
# zpool status tank
  pool: tank
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            c2t0d0  ONLINE       0     0     0
            c2t1d0  ONLINE       0     0     0
            c2t3d0  ONLINE       0     0     0
        cache
          c2t5d0    ONLINE       0     0     0
          c2t8d0    ONLINE       0     0     0

errors: No known data errors

Review the following points when considering whether to create a ZFS storage pool with cache devices:

Using cache devices provide the greatest performance improvement for random read-workloads of mostly static content.
Capacity and reads can be monitored by using the zpool iostat command.
Single or multiple cache devices can be added when the pool is created or added and removed after the pool is created. For more information, see Example 4–4.
Cache devices cannot be mirrored or be part of a RAID-Z configuration.
If a read error is encountered on a cache device, that read I/O is reissued to the original storage pool device, which might be part of a mirrored or RAID-Z configuration. The content of the cache devices is considered volatile, as is the case with other system caches.