NPIV or Virtual SCSI- Which one is better?

Last days i was investigating about real difference between NPIV and Virtual SCSI options available on IBM Pseries platform for virtualisation implementation.Unfortunately i could not find that except that if you have a FC based tape library or any other tape device and you want to share it between your Lpars ( which is rear case in today's market as it is captured by enterprise backup solutions like TSM or Veritas which does not require this kind of setup) or when you want to avoid word SCSI in front of your management, you can opt NPIV approach otherwise vscsi approach is well established approach in terms of performance ad reliability.

However , for NPIV , following are minimum requirements:

1. Eight Gig FC Adapater ( NPIV capable)

2. NPIV capable SAN switches

3. VIO 2.1

So rule of thumb is that if you dont have above mentioned luxuries , you can stick to VSCSI approach.

 

Wpars versus Lpars- A quick comparision

While Lpars and Wpars are both virtualization features of IBM Power systems , there are inherently differences which do reside between Lpars and Wpars.

I would say a major difference which exist between Lpars and Wpars is that Lpars are hardware based virtualization approach while Wpars are software based approach.
WPARs are lightweight and quicker to install, because they share many of the file systems and resources of the global AIX system in which they reside.
On the other hand While using an LPAR requires you to install an entire operating system, creation of system WPARs only installs private copies of a few file systems, and application WPARs share even more of the global system's resources. As a result, a WPAR can be created in just a few minutes without installation media. Ongoing administration and maintenance of WPARs should be simpler—fewer AIX licenses might be required, and you don’t have to install fixes and updates on so many virtual systems. There is a command for synchronizing the filesets of a WPAR with the corresponding filesets on the global system, so you have the choice of propagating AIX fixes to WPARs or continuing to run with the current versions of system files.

While LPARs offer a significantly higher degree of workload isolation, WPARs might provide "good enough" isolation for your particular workloads, especially temporary ones such as development or test environments. Similarly, with LPARs, you can achieve a greater degree of control over the usage of resources—by allocating entire processors or precise fractions of processors to an LPAR, for example. With WPARs, you don’t have such fine control over resource allocations, but you can allocate target shares or percentages of CPU utilization to a WPAR (if have used the AIX Workload Manager, you will find the share and percentage resource allocation scheme familiar). Similar differences exist for the allocation of memory, number of processes, and other resources.