My current project is about making an accounting engine that handles all
the journal entries, transactions, portfolios etc. The communication
with the engine is based on simple protocol, the things to be taken
care of in the order are consistency, handling large data(performance) and availability.

I came across a video lecture by Simon Peyton Jones where he gives an example from Financial domain (derivatives etc) to explain how haskell is being used and the advantages provided.

I am interested in knowing if Haskell will be the right fit for my project. My requirements are transactional nature, which I believe is one of the strengths of functional programming, also handling large data set and being available. there is no such requirement for partitioning of data and the application is going to be centrally hosted on a single server.

AFAIK OCaml and other functional languages are heavily used in financial domain, some of the reason are same as features I am looking for.
I wanted some insight as to how Haskell is going to help me with my project. Also there has been some concerns because of lazy evaluation in Haskell and memory leaks associated with it. http://jlouisramblings.blogspot.com/2010/04/haskell-vs-erlang-for-bittorent-clients.html

Also, if you have any suggestions of the choice of programming
language, we have been looking into other functional languages like
 Scala and Clojure. But we have not dig deep on the performance
aspects of these languages, if someone can shed a light on the pros-
cons of these languages, it will help us very much to come to a
decision.

-Regards,
Amir