Information Technology Reference
In-Depth Information
Direct LUN mapping
Like sharing disk, users can also attach direct LUNs to virtual machines in Red Hat Enter-
prise Virtualization, which allow for the same sharing as a normal disk image. The LUN
from the SAN is connected to the hypervisor hosting the virtual machines via a host bus ad-
apter of the host through which all the storage I/O takes place. A
LUN
is a number used to
identify a logical unit related to computer storage. A logical unit is a device addressed by
protocols and related to fiber channel,
Small Computer System Interface
(
SCSI
),
Inter-
net SCSI
(
iSCSI
), and other comparable interfaces.
There are a few considerations that the end user has to keep in mind before using the direct
LUN on virtual machines:
• Direct LUN from the storage must be presented to all the hosts in the data center
for the live migration of the virtual machine attached with direct LUN to work.
• Exporting virtual machine direct LUN disk to RHEV export domain is not suppor-
ted. Export of such virtual machines only exports other disks except the direct
LUN.
• Live storage migration of virtual machine direct LUN is not supported, while other
disks of such virtual machine can be moved across storage domains.
• Direct LUN will not be a part of virtual machine snapshots.
So, to attach a direct LUN from the storage to virtual machine, please follow these steps:
1. Log in to the
Administrator
console and navigate to the
Disks
tab.
2. Click on
Add
to open the
Add Virtual Disk
window and select
External (Direct
Lun)
on the upper-right side of the window.
3. Insert some meaningful content in the
Alias
and
Description
fields; leave the
In-
terface
field as
Virtio
, select
Data Center
from the drop-down menu, choose the
host from the
Use Host
drop-down menu, and set the storage type to either
iSCSI
or
Fibre Channel
based on what is relevant to your environment.
This will result in immediate scanning of all the LUNs visible to the selected host
and display the list of available LUNs to use from the storage as mentioned in the
following screenshot.
4. Select the LUN. You can optionally choose
Is Bootable
and
Is Shareable
if there
is a need to present this direct LUN in the sharing mode to multiple virtual ma-
chines that run any high-availability cluster applications. Finally, click on
OK
to
create a new direct LUN and close the window.
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