mkvdiskhostmap
Use the mkvdiskhostmap command to create a new mapping between a volume and a host, which makes the volume accessible for input/output (I/O) operations to the specified host.
Syntax
Parameters
- -force
- (Optional) Allows multiple volume-to-host assignments, which are not normally allowed.
- -host host_id | host_name
- (Required) Specifies the host to map the volume to, either by ID or by name.
- -scsi scsi_num_arg
- (Optional) Specifies the Small Computer System Interface (SCSI) logical unit number (LUN) ID to assign to this volume on the given host. The scsi_num_arg parameter contains the SCSI LUN ID that is assigned to the volume on the given host for all I/O groups that provide access to the volume. You must check your host system for the next available SCSI LUN ID on the given host bus adapter (HBA). If you do not specify the -scsi parameter, the next available SCSI LUN ID in each I/O group that provides access to the host. The -scsi parameter is not supported for NVMe hosts. When a volume is mapped to a host that uses the NVMe protocol, the volume namespace ID (NSID) is assigned by the system. This parameter is mutually exclusive with -allowmismatchedscsiids.
- -allowmismatchedscsiids
- (Optional) When you create a new host mapping, this parameter allows the system to allocate non-identical SCSI LUN IDs in access I/O groups for the volume. This parameter is mutually exclusive with -scsi.
- vdisk_name | vdisk_id
- (Required) Specifies the name of the volume that you want to map to the host, either by ID or by name.
Description
This command creates a new mapping between the volume and the specified host. The volume is presented to the host as if the disk is directly attached to the host. It is only after this command is processed, that the host can perform I/O transactions to the volume.
Optionally, you can assign a SCSI LUN ID to the mapping for SCSI hosts. When the HBA in the host
scans for devices that are attached to it, it discovers all volumes that are mapped to its Fibre
Channel ports. When the devices are found, each one is allocated an identifier (SCSI LUN ID). For
example, the first disk found is usually SCSI LUN 0
, and so on. You can control the
order in which the HBA discovers volumes by assigning the SCSI LUN ID, as required. If you do not
specify a SCSI LUN ID, the cluster automatically assigns the next available SCSI LUN ID, if any
mappings already exist with that host. When you issue the mkvdiskhostmap command,
the assigned SCSI LUN ID number is returned.
For NVMe, the SCSI LUN ID is irrelevant and instead the system assigns the NSID that cannot be changed. When you create a mapping to an NVMe volume, the NSID is returned (The NSID is the vdisk_ID + 1).
- Host to which this mapping is being made is not associated with any one of the I/O groups in the volume access set
- Volume has more than one I/O group in its access set and the host being mapped to the volume does not support volumes being mapped from multiple I/O groups
- Host protocol is incompatible with the volume protocol
- An identical SCSI LUN ID is not available in all the access I/O groups.
The returned ID is same for the I/O groupall I/O groups to which the volume is mapped.
Use the -allowmismatchedscsiids parameter to allow the system to allocate non-identical SCSI LUN IDs in the access I/O groups. The lowest value available in each access I/O group is used and the value might not be the same in all access I/O groups. Make sure that the host supports this configuration. This parameter cannot be used with the -scsi parameter and is not supported for NVMe hosts. If a volume is mapped to a host that uses the NVMe protocol, the volume namespace ID (NSID) is assigned by the system.
If you generate different SCSI LUN IDs, only one is returned. The returned ID is for the highest-numbered I/O group to which the volume was mapped. To view other values, issue lshostvdiskmap or lsvdiskhostmap.
The SCSI LUN ID is used for the highest numbered I/O group to which the volume is mapped.
- Volume 1 is mapped to Host 1 with SCSI LUN ID 1
- Volume 2 is mapped to Host 1 with SCSI LUN ID 2
- Volume 3 is mapped to Host 1 with SCSI LUN ID 4
When the device driver scans the HBA, it must stop after identifying volumes 1
and
2
, because no SCSI LUN is mapped with ID 3. For optimal performance, ensure that the SCSI LUN ID allocation
is contiguous.
mkvdiskhostmap -host host1 -force 4 mkvdiskhostmap -host host2 -force
4
.These commands create two host-to-volume mappings for volume 4
that map to
host1
and host2
. Omitting the -force
parameter causes the mapping to fail if that volume is already mapped to a host.
The command also fails if the host object (to which this mapping is being made) is not associated with the I/O group containing the volume.
- Mapping is created for configuration purposes (it can be changed or deleted)
- Secondary volume is not presented to the host
- Host type is changed to a type other than hide_secondary
- Remote copy relationship is stopped by specifying -access
- Volume is no longer a secondary volume because the remote copy relationship is deleted or switched
An invocation example
mkvdiskhostmap -host host1 -scsi 1 5
The resulting output:
Virtual Disk to Host map, id [1], successfully created