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Advanced POWER Virtualization on IBM System p5 - Previous ...

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►<br />

The value propositi<strong>on</strong> enabling <strong>on</strong> demand computing and server<br />

c<strong>on</strong>solidati<strong>on</strong>. Virtual I/O also provides a more ec<strong>on</strong>omic I/O model by using<br />

physical resources more efficiently through sharing.<br />

At the time of writing, the virtualizati<strong>on</strong> features of the <strong>IBM</strong> <strong>System</strong> p platform<br />

support up to 254 partiti<strong>on</strong>s, while the server hardware provides up to 240 I/O<br />

slots and 192 internal SCSI disks per machine. With each partiti<strong>on</strong> typically<br />

requiring <strong>on</strong>e I/O slot for disk attachment and another <strong>on</strong>e for network<br />

attachment, this puts a c<strong>on</strong>straint <strong>on</strong> the number of partiti<strong>on</strong>s. To overcome these<br />

physical requirements, I/O resources have to be shared. Virtual SCSI provides<br />

the means to do this for SCSI storage devices.<br />

<strong>IBM</strong> supports up to ten Virtual I/O Servers within a single CEC managed by an<br />

HMC. Though architecturally up to 254 LPARS are supported, more than ten<br />

Virtual I/O Server LPARs within a single CEC have not been tested and therefore<br />

are not recommended.<br />

Note: You will see different terms in this redbook that refer to the various<br />

comp<strong>on</strong>ents involved with virtual SCSI. Depending <strong>on</strong> the c<strong>on</strong>text, these<br />

terms may vary. With SCSI, usually the terms initiator and target are used, so<br />

you may see terms such as virtual SCSI initiator and virtual SCSI target. On<br />

the HMC, the terms virtual SCSI server adapter and virtual SCSI client<br />

adapter are used. Basically, they refer to the same thing. When describing the<br />

client/server relati<strong>on</strong>ship between the partiti<strong>on</strong>s involved in virtual SCSI, the<br />

terms hosting partiti<strong>on</strong> (meaning the Virtual I/O Server) and hosted partiti<strong>on</strong><br />

(meaning the client partiti<strong>on</strong>) are used.<br />

2.9.1 Partiti<strong>on</strong> access to virtual SCSI devices<br />

The following secti<strong>on</strong>s describe the virtual SCSI architecture and the protocols<br />

used.<br />

Virtual SCSI client and server architecture overview<br />

Virtual SCSI is based <strong>on</strong> a client/server relati<strong>on</strong>ship. The Virtual I/O Server owns<br />

the physical resources and acts as server or, in SCSI terms, target device. The<br />

logical partiti<strong>on</strong>s access the virtual SCSI resources provided by the Virtual I/O<br />

Server as clients.<br />

The virtual I/O adapters are c<strong>on</strong>figured using an HMC or through Integrated<br />

<str<strong>on</strong>g>Virtualizati<strong>on</strong></str<strong>on</strong>g> Manager <strong>on</strong> smaller systems. The provisi<strong>on</strong>ing of virtual disk<br />

resources is provided by the Virtual I/O Server.<br />

Often the Virtual I/O Server is also referred to as a hosting partiti<strong>on</strong> and the client<br />

partiti<strong>on</strong>s as hosted partiti<strong>on</strong>s.<br />

90 <str<strong>on</strong>g>Advanced</str<strong>on</strong>g> <str<strong>on</strong>g>POWER</str<strong>on</strong>g> <str<strong>on</strong>g>Virtualizati<strong>on</strong></str<strong>on</strong>g> <strong>on</strong> <strong>IBM</strong> <strong>System</strong> <strong>p5</strong>

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