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.Dd May 26, 2021
.Dt VDEV_ID.CONF 5
.Os
.
.Sh NAME
.Nm vdev_id.conf
.Nd Configuration file for vdev_id
.Sh DESCRIPTION
.Nm
is the configuration file for
.Nm vdev_id Ns Sy (8) .
It controls the default behavior of
.Nm vdev_id Ns Sy (8)
while it is mapping a disk device name to an alias.
.Pp
The
.Nm
file uses a simple format consisting of a keyword followed by one or
more values on a single line.
Any line not beginning with a recognized keyword is ignored.
Comments may optionally begin with a hash character.
.Pp
The following keywords and values are used.
.Bl -tag -width "-h"
.It Sy alias Ar name Ar devlink
Maps a device link in the
.Pa /dev
directory hierarchy to a new device name.
The udev rule defining the device link must have run prior to
.Nm vdev_id Ns Sy (8) .
A defined alias takes precedence over a topology-derived name, but the
two naming methods can otherwise coexist.
For example, one might name drives in a JBOD with the
.Sy sas_direct
topology while naming an internal L2ARC device with an alias.
.Pp
.Ar name
is the name of the link to the device that will by created under
.Pa /dev/disk/by-vdev .
.Pp
.Ar devlink
is the name of the device link that has already been
defined by udev.
This may be an absolute path or the base filename.
.
.It Sy channel [ Ns Ar pci_slot ] Ar port Ar name
Maps a physical path to a channel name (typically representing a single
disk enclosure).
.
.It Sy enclosure_symlinks Sy yes Ns | Ns Sy no
Additionally create
.Pa /dev/by-enclosure
symlinks to the disk enclosure
.Em sg
devices using the naming scheme from
.Pa vdev_id.conf .
.Sy enclosure_symlinks
is only allowed for
.Sy sas_direct
mode.
.
.It Sy enclosure_symlinks_prefix Ar prefix
Specify the prefix for the enclosure symlinks in the form
.Pa /dev/by-enclosure/ Ns Ao Ar prefix Ac Ns - Ns Ao Ar channel Ac Ns Aq Ar num
.Pp
Defaults to
.Dq Em enc .
.
.It Sy slot Ar prefix Ar new Op Ar channel
Maps a disk slot number as reported by the operating system to an
alternative slot number.
If the
.Ar channel
parameter is specified
then the mapping is only applied to slots in the named channel,
otherwise the mapping is applied to all channels.
The first-specified
.Ar slot
rule that can match a slot takes precedence.
Therefore a channel-specific mapping for a given slot should generally appear
before a generic mapping for the same slot.
In this way a custom mapping may be applied to a particular channel
and a default mapping applied to the others.
.
.It Sy multipath Sy yes Ns | Ns Sy no
Specifies whether
.Nm vdev_id Ns Sy (8)
will handle only dm-multipath devices.
If set to
.Sy yes
then
.Nm vdev_id Ns Sy (8)
will examine the first running component disk of a dm-multipath
device as provided by the driver command to determine the physical path.
.
.It Sy topology Sy sas_direct Ns | Ns Sy sas_switch Ns | Ns Sy scsi
Identifies a physical topology that governs how physical paths are
mapped to channels:
.Bl -tag -compact -width "sas_direct and scsi"
.It Sy sas_direct No and Sy scsi
channels are uniquely identified by a PCI slot and HBA port number
.It Sy sas_switch
channels are uniquely identified by a SAS switch port number
.El
.
.It Sy phys_per_port Ar num
Specifies the number of PHY devices associated with a SAS HBA port or SAS
switch port.
.Nm vdev_id Ns Sy (8)
internally uses this value to determine which HBA or switch port a
device is connected to.
The default is
.Sy 4 .
.
.It Sy slot Sy bay Ns | Ns Sy phy Ns | Ns Sy port Ns | Ns Sy id Ns | Ns Sy lun Ns | Ns Sy ses
Specifies from which element of a SAS identifier the slot number is
taken.
The default is
.Sy bay :
.Bl -tag -compact -width "port"
.It Sy bay
read the slot number from the bay identifier.
.It Sy phy
read the slot number from the phy identifier.
.It Sy port
use the SAS port as the slot number.
.It Sy id
use the scsi id as the slot number.
.It Sy lun
use the scsi lun as the slot number.
.It Sy ses
use the SCSI Enclosure Services (SES) enclosure device slot number,
as reported by
.Xr sg_ses 8 .
Intended for use only on systems where
.Sy bay
is unsupported,
noting that
.Sy port
and
.Sy id
may be unstable across disk replacement.
.El
.El
.
.Sh FILES
.Bl -tag -width "-v v"
.It Pa /etc/zfs/vdev_id.conf
The configuration file for
.Nm vdev_id Ns Sy (8) .
.El
.
.Sh EXAMPLES
A non-multipath configuration with direct-attached SAS enclosures and an
arbitrary slot re-mapping:
.Bd -literal -offset Ds
multipath     no
topology      sas_direct
phys_per_port 4
slot          bay

#       PCI_SLOT HBA PORT  CHANNEL NAME
channel 85:00.0  1         A
channel 85:00.0  0         B
channel 86:00.0  1         C
channel 86:00.0  0         D

# Custom mapping for Channel A

#    Linux      Mapped
#    Slot       Slot      Channel
slot 1          7         A
slot 2          10        A
slot 3          3         A
slot 4          6         A

# Default mapping for B, C, and D

slot 1          4
slot 2          2
slot 3          1
slot 4          3
.Ed
.Pp
A SAS-switch topology.
Note, that the
.Ar channel
keyword takes only two arguments in this example.
.Bd -literal -offset Ds
topology      sas_switch

#       SWITCH PORT  CHANNEL NAME
channel 1            A
channel 2            B
channel 3            C
channel 4            D
.Ed
.Pp
A multipath configuration.
Note that channel names have multiple
definitions - one per physical path.
.Bd -literal -offset Ds
multipath yes

#       PCI_SLOT HBA PORT  CHANNEL NAME
channel 85:00.0  1         A
channel 85:00.0  0         B
channel 86:00.0  1         A
channel 86:00.0  0         B
.Ed
.Pp
A configuration with enclosure_symlinks enabled.
.Bd -literal -offset Ds
multipath yes
enclosure_symlinks yes

#          PCI_ID      HBA PORT     CHANNEL NAME
channel    05:00.0     1            U
channel    05:00.0     0            L
channel    06:00.0     1            U
channel    06:00.0     0            L
.Ed
.Pp
In addition to the disks symlinks, this configuration will create:
.Bd -literal -offset Ds
/dev/by-enclosure/enc-L0
/dev/by-enclosure/enc-L1
/dev/by-enclosure/enc-U0
/dev/by-enclosure/enc-U1
.Ed
.Pp
A configuration using device link aliases.
.Bd -literal -offset Ds
#     by-vdev
#     name     fully qualified or base name of device link
alias d1       /dev/disk/by-id/wwn-0x5000c5002de3b9ca
alias d2       wwn-0x5000c5002def789e
.Ed
.
.Sh SEE ALSO
.Xr vdev_id 8