Native Properties

Every vdev has a set of properties that export statistics about the vdev as well as control various behaviors. Properties are not inherited from top-level vdevs, with the exception of checksum_n, checksum_t, io_n, io_t, slow_io_n, and slow_io_t.

The values of numeric properties can be specified using human-readable suffixes (for example, k, KB, M, Gb, and so forth, up to Z for zettabyte). The following are all valid (and equal) specifications: 1536M, 1.5g, 1.50GB.

The values of non-numeric properties are case sensitive and must be lowercase.

The following native properties consist of read-only statistics about the vdev. These properties can not be changed.

capacity

Percentage of vdev space used

state

state of this vdev such as online, faulted, or offline

guid

globally unique id of this vdev

asize

The allocable size of this vdev

psize

The physical size of this vdev

ashift

The physical sector size of this vdev expressed as the power of two

size

The total size of this vdev

free

The amount of remaining free space on this vdev

allocated

The amount of allocated space on this vdev

expandsize

How much this vdev can expand by

fragmentation

Percent of fragmentation in this vdev

parity

The level of parity for this vdev

devid

The device id for this vdev

physpath

The physical path to the device

encpath

The enclosure path to the device

fru

Field Replacable Unit, usually a model number

parent

Parent of this vdev

children

Comma separated list of children of this vdev

numchildren

The number of children belonging to this vdev

read_errors, write_errors, checksum_errors, initialize_errors

The number of errors of each type encountered by this vdev

null_ops, read_ops, write_ops, free_ops, claim_ops, trim_ops

The number of I/O operations of each type performed by this vdev

null_bytes, read_bytes, write_bytes, free_bytes, claim_bytes, trim_bytes

The cumulative size of all operations of each type performed by this vdev

removing

If this device is currently being removed from the pool

The following native properties can be used to change the behavior of a vdev.

checksum_n, checksum_t, io_n, io_t, slow_io_n, slow_io_t

Tune the fault management daemon by specifying checksum/io thresholds of <N> errors in <T> seconds, respectively. These properties can be set on leaf and top-level vdevs. When the property is set on the leaf and top-level vdev, the value of the leaf vdev will be used. If the property is only set on the top-level vdev, this value will be used. The value of these properties do not persist across vdev replacement. For this reason, it is advisable to set the property on the top-level vdev - not on the leaf vdev itself. The default values for OpenZFS on Linux are 10 errors in 600 seconds. For OpenZFS on FreeBSD defaults see zfsd(8).

comment

A text comment up to 8192 characters long

bootsize

The amount of space to reserve for the EFI system partition

failfast

If this device should propage BIO errors back to ZFS, used to disable failfast.

path

The path to the device for this vdev

allocating

If this device should perform new allocations, used to disable a device when it is scheduled for later removal. See zpool-remove(8).

User Properties

In addition to the standard native properties, ZFS supports arbitrary user properties. User properties have no effect on ZFS behavior, but applications or administrators can use them to annotate vdevs.

User property names must contain a colon (":") character to distinguish them from native properties. They may contain lowercase letters, numbers, and the following punctuation characters: colon (":"), dash ("-"), period ("."), and underscore ("_"). The expected convention is that the property name is divided into two portions such as module:property, but this namespace is not enforced by ZFS. User property names can be at most 256 characters, and cannot begin with a dash ("-").

When making programmatic use of user properties, it is strongly suggested to use a reversed DNS domain name for the module component of property names to reduce the chance that two independently-developed packages use the same property name for different purposes.

The values of user properties are arbitrary strings and are never validated. Use the zpool set command with a blank value to clear a user property. Property values are limited to 8192 bytes.