Advanced Storage and Networking Features - Getting Started with Red Hat Enterprise Virtualization - page 119

Shareable disks
The floating disk or shareable disks feature of Red Hat Enterprise Virtualization will allow
you to carve out a new virtual disk with the shareable option enabled. Virtual disks marked
shareable are independent of any virtual machines and can be attached to a single or mul-
tiple numbers of virtual machines. This will be useful in scenarios where an application re-
quires storage to be shared across virtual machines and integrated with high-availability
cluster software on those virtual machines to create a group of cluster nodes with shared
storage access.
Please be careful while using floating disks. Using shareable disks and mounting the shared
disks across multiple virtual machines at the same time (without using any cluster-aware
software to coordinate disk read and write of the mounted file system) leads to data corrup-
tion. For example, you can use floating disks across two virtual machines and build an act-
ive/passive cluster service using Red Hat's high-availability add-on, or you can share it
across three virtual machines and integrate it with the cluster filesystem, such as Red Hat
Global File System 2 ( GF2 ) for simultaneous read/write across all three nodes using the
floating disk as a shared storage.
You can create a new sharing disk, or mark any of the existing disks as a sharing disk and
attach it to the virtual machine. To create a new sharing disk, perform the following 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 you will see that by de-
fault, Internal is selected on the upper-left side of the window; leave it as it is.
3. Insert the disk size in the Size (GB) field, and then insert some meaningful content
in the Alias and Description fields. Leave the Interface field as Virtio and Alloc-
ation policy as Preallocated . Select Data Center from the drop-down menu, se-
lect the respective storage domain from the drop-down menu, and leave the Quota
field as the default value Quota_Admin .
4. On the top-right hand corner of the same window, select the Is Shareable and
Wipe After Delete options. Finally, click on OK to create the virtual disk and
close the window.