APC RAID Subsystem SCSI-SATA II Informações Técnicas descarregar pdf (Página 120)

Advanced Functions

5-2

If directly attaching the host-interface ports to the HBAs, you can easily know the number of paths for single virtual disk by

counting the physical links. But if a switch is used to build a fabric, you need to multiply the number of HBA ports and the

number of host-interface ports of the controller to derive the number of paths. For example, if a host has three HBA ports

connecting to a switch, which links to a RAID system with four host-interface ports, there will be twelve paths for the host

to the RAID system.

For regular operating systems, a path is perceived as a physical disk, and accessing a LUN through different paths

simultaneously without multi-path software could cause data corruption. It is the multi-path software to scan all detected

physical disks (paths) and map the physical disks to single logical disk (MPIO disk) if these physical disks present

consistent information to indicate that they belong to the same virtual disk. The applications then can access the LUN via

the MPIO disk.

After completing the physical connections between hosts and RAID systems, please follow the steps below:

1. Create virtual disks, like JBOD disks, logical disks, and volumes

2. Choose symmetric storage presentation method

3. Add all HBA ports (with WWPN or SAS address) to the hosts in the controller

4. Selectively add hosts (HBA ports) to a host group (HG)

5. Export virtual disks to LUNs for the host group (HG)

6. Repeat the previous two steps for each host computer and host group

The hosts mentioned in this manual and the user interfaces of the RAID systems refer to the HBA ports on the host

computers, and host groups refer to a group of HBA ports. For example, a host computer with two dual-port HBAs is

perceived as four individual hosts by the RAID controller. Exporting a virtual disk to a host or a host group will allow the

HBA port or the group of HBA ports to access the virtual disks from any of the host-interface ports in the RAID system.

Bellow is the guideline and example to set up the hosts and host groups when using multi-path IO solutions:

• Independent MPIO Hosts Computers

For independent (non-clustered) host computers sharing

single RAID system, the storage should be partitioned

and accessed independently by the host computers. One

host group should be created for each host computer,

and the host group should include all HBA ports on the

host computer. So, each host computer has LUN

mappings of its own, and it can see its LUN mappings

from all HBA ports and paths.

Figure 5-26 illustrates two independent servers sharing

single RAID system with multi-path I/O. Each server sees

two LUNs (DG0LD0 and DG0LD1 for Server 1, and

DG1LD0 and DG1LD1 for Server 2), each of which has

two paths.

The table below shows the configuration steps for Figure

5-26.

Note

1. Because a LUN is not accessible during regular initialization, install the MPIO driver after the

regular initialization is done or use background initialization.

2. Use MPIO management utility to verify that all disk devices and paths are recognized by the

MPIO software.

3. Go to Section 5.2 when using MPIO with redundant-controller systems.

FCP1FCP2FCP2 FCP1

Storage Group 0

(for Host Group 0)

Storage Group 1

(for Host Group 1)

LUN0

(DG0LD0)

LUN1

(DG0LD1)

LUN2

(DG1LD0)

LUN3

(DG1LD1)

1 2 3 4 5 6

7 8 9 10 11 12

Server1

(with Pathguard installed)

Server2

(with Pathguard installed)

WWPN

HBA1

HBA0

HBA3

HBA2

Host Group 0 Host Group 1

Fibre Switch

(SAN)

Figure 5-1 Dual independent MPIO hosts

1 2 ... 115 116 117 118 119 120 121 122 123 124 125 ... 258 259

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