It seems that every time that IBM releases a new server line, Timothy Prickett 
Morgan and itjungle.com releases a series of articles comparing IBM i 
price/performance against Unix, Windows, and Linux alternatives.  IBM i 
platforms normally take a beating in terms of price/performance.  TPM is 
continuously hammering IBM on it.  One notable exception is the new model 720, 
which beat Unix and Windows alternatives in recent comparisons.  But when it 
comes to Linux, TPM makes a point about IBM i user based licensing driving up 
the cost of a model 720 against Linux, Intel, and open-source databases, which 
don't have user based pricing.
http://www.itjungle.com/tfh/tfh110810-story01.html
I think I understand what a user is under IBM i.  It's an individual who 
exchanges credentials with IBM i; one who has a user profile, or authenticates 
against a validation list or LDAP entry. And one who is entitled to use software 
like IBM i Access, Navigator, Systems Director, Web Admin, TCP/IP servers, etc. 
  But what is a user under Linux and say Postgre SQL?  Is TPM's comparison 
valid?
-Nathan
      
As an Amazon Associate we earn from qualifying purchases.