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This article will explain in detail the example analysis of IBM storage multipath software. The content of the article is of high quality, so the editor will share it with you for reference. I hope you will have some understanding of the relevant knowledge after reading this article.

Multipath software belongs to the driver layer. A lun is mapped to the host through multiple links and will be recognized as multiple hdisk. The principle of multipath software is to integrate these hdisk into a usable disk.

Ordinary computer mainframe is a hard disk attached to a bus, here is an one-to-one relationship. When it comes to the SAN environment composed of optical fiber, or the IPSAN environment composed of iSCSI, because the host and storage are connected through the optical fiber switch or multiple network cards and IP, then it constitutes a many-to-many relationship. That is, there can be multiple paths from the host to the storage. The IO from the host to the storage can be selected by multiple paths. Each host can go through several different paths to the corresponding storage. If it is used at the same time, how is the Icano traffic allocated? One of the paths is broken, how to deal with it? And from the operating system's point of view, each path will be regarded as an actual physical disk, but in fact it is only a different path to the same physical disk, which brings confusion to the user when using it. Multipath software came into being to solve the above problems. The main function of multipathing is to work with storage devices to achieve the following functions:

1. Failure switching and recovery

2. Load balancing of IO traffic

3. Virtualization of disk

Because multipath software needs to be used in conjunction with storage, different vendors provide different versions based on different operating systems. And some manufacturers, software and hardware are not sold together, if you want to use multipath software, you may need to buy license from manufacturers. For example, EMC's multipath software based on linux needs to buy license separately. Fortunately, the kernel of RedHat and Suse 2.6 comes with a free multipath package that can be used for free, and it is also a general-purpose package that can support devices from most storage vendors, even if some are not well-known vendors, they can support and run well by making minor changes to the configuration file.

1. Before the aix system of ibm, the default multipath software is rdac, so there is only one path from the host to each controller.

2. After aix6.1, the multipath software installed by default is mpio.

Multipathing supported by IBM storage:

DS3000: native MPIOonly

DS4000: RDAC, native MPIO, MPIO w/SDDPCM

DS5000: native MPIO, MPIO w/SDDPCM

The following command allows you to view the multipathing used by the current system:

# manage_disk_drivers

1: DS4100: currently MPIO; supported: RDAC/fcparray, MPIO

2: DS4300: currently MPIO; supported: RDAC/fcparray, MPIO

3: DS4500: currently MPIO; supported: RDAC/fcparray, MPIO

4: DS4700/DS4200: currently MPIO; supported: RDAC/fcparray, MPIO

5: DS4800: currently MPIO; supported: RDAC/fcparray, MPIO

3. SDD and SDDPCM can be used as host multipath software for high-end storage of IBM.

SDDPCM is an aix module that makes MPIO support IBM's ESS800/DS6000/DS8000/SVC.

Similarly, there is also MPIO under windows, and the module that enables MPIO on windows to support ESS800/DS6000/DS8000/SVC is called SDDDSM

SDDPCM/SDDDSM is just a module, and you also need to enable the MPIO feature of native.

It can be seen from ibm sdd support matrix

Support Matrix for AIX SDD

Support Matrix for Windows SDD

Support Matrix for Linux SDD

Support Matrix for HP SDD

Support Matrix for Solaris SDD

Support Matrix for Novell SDD

Support Matrix for AIX SDDPCM

Support Matrix for Windows SDDDSM

Support Matrix for Linux DM-Multipath

IBM is a multipath software stored on different systems. PCM and DSM can only be used under aix and windows. (SDDPCM must use MPIO in AIX, SDDSCM use in windows)

AIX6.1 comes with MPIO by default. The devices you see in lsdev are as follows:

# lsdev-Cc disk

Hdisk0 Available 00-08-00 SAS Disk Drive

Hdisk1 Available 00-08-00 SAS Disk Drive

Hdisk2 Available 04-00-01 MPIO other FC disk

Hdisk3 Available 04-00-01 MPIO other FC disk

Hdisk4 Available 04-00-01 MPIO other FC disk

Hdisk5 Available 04-00-01MPIO other FC disk

Hdisk6 Available 04-00-01 MPIO other FC disk

After installing SDDPCM, the devices you see in lsdev are as follows:

# lsdev-Cc disk

Hdisk0 Available 00-08-00 SAS Disk Drive

Hdisk1 Available 00-08-00 SAS Disk Drive

Hdisk2 Available 04-00-01 IBM MPIO FC 1750

Hdisk3 Available 04-00-01 IBM MPIO FC 1750

Hdisk4 Available 04-00-01 IBM MPIO FC 1750

Hdisk5 Available 04-00-01 IBM MPIO FC 1750

Hdisk6 Available 04-00-01 IBM MPIO FC 1750

In addition, in both cases, lspv displays hdisk:

# lspv

Hdisk0 00f64cd35ba7253f rootvg active

Hdisk1 00f64cd3743abfeb rootvg active

Hdisk2 00f64cd3744116ff None

Hdisk3 00f64cd3744117ef None

Hdisk4 00f64cd674693920 None

Hdisk5 none None

Hdisk6 none None

The sddpcm packages that support AIX6.1 are:

Devices.sddpcm.61.2.4.0.2.bff

Devices.sddpcm.61.rte

Devices.fcp.disk.ibm.mpio.rte

The SDDPCM fileset also provides thesddpcm_get_configcommand for DS4000/DS5000 devices which displays information about all MPIO-based DS4K/DS5K subsystems

# sddpcm_get_config-Av

Frame. Id 0:

Storage Subsystem worldwide name: 60ab8001143a0000049b88968

Controller count: 2

Partition count: 1

Partition 0:

Storage Subsystem Name = 'VIOS_DS4800'

Hdisk LUN # Ownership User Label

Hdisk3 0 A (non-preferred) lpar3_vol01

This is the end of the sample analysis of IBM storage multipath software. I hope the above content can be helpful to you and learn more knowledge. If you think the article is good, you can share it for more people to see.

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