Virtual Fibre Channel for NPIV Requires Memory too!
nagger 100000MRSJ Comments (3) Visits (13130)
So we use what has become known as Austin's Rule of Thumb = 140 MB per virtual Fibre Channel adapter - this is additional Hypervisor memory but I am not sure who Austin is :-) This is memory you should allow for when sizing or designing a POWER machine as an administrator does not allocate memory to the Hypervisor - it just grabs what it needs.
With, say, just two physical adapters connected by NPIV to a small handful of client Virtual Machines you may have already configured enough memory in the machine. Most people are allowing in a sizing activity 2 to 4 GB of memory in a VIOS these days on larger machines, some in the VIOS itself and some as the Hypervisor memory.
Larger configurations of NPIV clients need to be calculated. For example: two VIOS supporting 20 client VMs, each client has one virtual Fibre Channel adapter on each VIOS = 40 virtual Fibre Channel adapters at 140 MB each = 5.6 GB memory. That might be a shock! But if you compare that to 40 physical Fibre Channel adapters, you will need 20GB of memory (see other blog entry). So virtual is still a winner in just memory terms.
Of course, virtual also wins in
Hope this helps, thanks, Nigel