Lync standard 2013 deployment with standard SQL 2008/2012

Question

Hi 
I have been looking into the requirements and of setup Lync 2013 and I'm getting a little confused at to what would be required for SQL databases and what servers they need to be located on. 
we have two sites siteA and siteB and a fast link between them 1g 
I want to have two FE lync servers at site A in a pool 
I want to have two FE Lync servers at site B in a pool
want to have the DR capabilities that have been mentioned in pool pairing as well can this be done with standard only 
Do I require SQL for these Front end servers? or do I just need two BE servers at each location each with SQL standard installed?
To start with we really only want to use lync for IM and Presence but will require access from Iphones will this require a edge server in the DMZ? or could you use TMG? 
what other roles will be required if we need to look at conversation that occurred in IM for auditing purposes. 
I have looked on Technet and it only really refers to using SQL express  for standard, which to me historically is something I have not done since it has been looked upon as free and therefore maybe not seen as an medium enterprise solution. 
thanks in advanced 
J

Answer 1

If you're using Standard edition servers, meaning you'd have 1 server per pool and you'd pair between the sites, no SQL licensing is required unless you want it for monitoring or persistent chat databases.
If you want to have multiple servers in a pool for high availability (you mentioned 2 per pool, you want a minimum of 3 per pool), you'll need a Lync Enterprise pool with a full SQL backend.
You can pool pair with both Standard and Enterprise.
You don't require SQL for the front ends in either scenario, as SQL Express will be installed.  For the Enterprise edition pool you'll need at least one SQL Standard instance, but a second for high availability using mirroring would be nice.  You'll
want a third SQL server acting as a witness to allow for automatic failover within the mirror, but this can be SQL express and doesn't require a license. 
For access from an iPhone, using the Lync mobility client, you'll need an edge for A/V traffic and a TMG or other reverse proxy such as IIS ARR or WAP to publish the web services on the front end pool to the Internet. 
Since this is Lync 2013, you don't need an additional role for auditing, auditing can be collocated on the front end server and write to the same SQL instance you're using for the front end pool.  You could also choose to keep the data in Exchange if
you're running at least Exchange 2013.
SQL express is the only thing you can use for Lync standard back end, but this isn't awful.  It does the job for Lync.  If you prefer a full SQL instance, then Enterprise is the way to go, and if you want HA with multiple servers in a pool, this
is your only option.  Lync will install SQL Express on each server regardless for local copies of the management store databases and presence information, but the primary copies will be in the full SQL back end instances. 
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This forum post is based upon my personal experience and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.