Impact of moving from Physical server to Virtual server.

[cognoslearner1]

Hi All,

We are planning to move from Physical server to Virtual server for Cognos. Does  this impact Cognos application in terms of performance ? Do we need to consider any important thing for this ?

Note : We are planning to move from physical to Virtual machine with same capacity.

Thanks,
Cognoslearner1.

[MFGF]

Hi All,

We are planning to move from Physical server to Virtual server for Cognos. Does  this impact Cognos application in terms of performance ? Do we need to consider any import thing for this ?

Note : We are planning to move from physical to Virtual machine with same capacity.

Thanks,
Cognoslearner1.

Generally virtual machines will not provide quite the same performance as if you are running on "bare metal" servers. A real CPU can be over-allocated, eg a physical server with 32 cores could be hosting four virtual servers, each with 12 virtual CPUs allocated (4x12 = 48). While an individual virtual machine may be specced appropriately, the underlying server might be overloaded and unable to fulfil the real hardware demands. The same is also true with memory. Even if this isn't the case, sometimes the virtualization software can introduce an extra overhead that needs to be taken into account (ie it requires CPU cycles and memory from the underlying server to provide the virtual machine environment). It's often not huge, but it's something to factor in.

Cheers!

MF.

[smiley]

http://www-01.ibm.com/support/docview.wss?uid=swg21425494

[johnwilkinson]

Also be aware of IBM restrictions regarding licensing on a virtualised environment. Any PVU licensed software needs to have the IBM license metric tool (ILMT) installed otherwise IBM will base your license position on the entire physical cluster. It can work out very expensive if you are caught out during an audit. I speak from bitter experience.