After you have properly installed HDLM, the LU configuration will change as follows:
- Before the installation of HDLM:
The host recognizes that a SCSI device is connected to each path.
Thus, a single LU in the storage system is recognized as though there are as many LUs as there are paths.
- After the installation of HDLM:
An HDLM device corresponding one-to-one with an LU in the storage system is created at a level higher than the SCSI device.#
Thus, from the host, LUs in the storage system are also recognized as a single LU regardless of the number of paths.
An LU recognized by a host after HDLM installation, is called a host LU (HLU). The areas in a host LU that correspond to the Dev (partition) in a storage system LU are called host devices (HDev).
On a system using HDLM, the logical device file for the HDLM device is used to access the target LU instead of the logical device file for the SCSI device.
The following figure shows the LU configuration recognized by the host, after the installation of HDLM.
The following table lists and describes the components recognized by the host.
Components |
Description |
|---|---|
HDev |
A Dev (partition) in an LU that the host recognizes via the HDLM driver. It is called a host device. One host device is recognized for one Dev in the storage system. |
HLU |
An LU that the host recognizes via the HDLM driver. It is called a host LU. Regardless of how many paths exist, only one host LU is recognized for each LU in the storage system. |