After registration of disks to a class other than the root class is complete, accessing the disks using physical special files as below becomes impossible. GDS prevents unintentional access by the users to physical special files in order to protect mirroring statuses.
/dev/sdXn (for normal hard disk) /dev/mapper/mpathXpn (for mpath devices of DM-MP) /dev/emcpowerXn (for emcpower devices) /dev/vdXn (for virtual disks on a KVM guest)
X indicates the device ID, and n is the slice number.
For example, if you execute the dd command to write to a disk using a physical special file, an error as below occurs.
# dd if=/dev/zero of=/dev/sda1 |
In the disk list output by the parted(8) command, disks that are registered to a class other than the root class are not displayed.
This access protection is canceled when a disk is removed from a class. It will also be canceled when an object is used for disk swap. The access protection function will turn back on if disk recovery operation is performed on the object.
Access to physical special files is prevented on the following nodes:
For disks that are registered in the shared class or the local class
When registered with the PRIMECLUSTER's resource database
All of the nodes in the relevant domains
When not registered with the PRIMECLUSTER's resource database
Access to the physical special files is prevented on the node where the local class is created.
For disks that are registered with shadow classes
Nodes where the relevant shadow classes reside
For the following disks, access to physical special files is not prevented. Be careful not to access these physical special files.
Disks that are registered in the root class
Disks that are registered with classes in other domains
Disks that are registered with root classes or local classes on other nodes and for which disk resources are not registered with the resource database
Disks that are registered with shadow classes on other nodes
When mirroring among servers, access to the physical special files is prevented only for iSCSI devices. As the configuration that "Figure 4.1 Disk setting for Performing Mirroring among Servers" shows, access to the physical special file of the iSCSI devices (sde and sdd) will be prevented but access to the physical special file of the physical disk (sdc) will not be prevented. Do not access the physical special file of the physical disk.
