Application and Data Server willl not communicate

We have an web application server,  MS SQL Server  and a data storage server(separate physical machines)
Our applications are written in PHP and classical ASP. The PHP uses the CodeIgniter framework.
The applications have always worked well.
Using the command line, at the data server, login  as administrator, I can access the data, read, write etc.
But  the web applications can not  - neither PHP or ASP - access the data storage server.
We use Windows Server 2012. We are using MS SQL 2008.
I am sure it is a permissions problem, and after viewing the event log on the data storage server.
It appears to be so since I am receiving "Login Failure - SMB session authentication failure" messages .
I am not sure of how set up permissions on the data storage server so the web applications can use it. I mean, I don't want to enter each person etc.
I am not finding much info on this problem.
Can someone guide me in what I need to check etc. to resolve this problem.
This is really urgent, any help appreciated.
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David Johnson, CD, MVPOwnerCommented:
check your web.config connectionsettings
Vitor MontalvãoMSSQL Senior EngineerCommented:
Check if the SQL Server account and the Application Account users have permissions on the SMB.
In case you don't know how to set permissions, this may depend on your storage solution. Here's an article that I hope it can help you.
dogsareitAuthor Commented:
Thank you both for responding. It is appreciated.

David -
 A valid point !
Although I know Windows Server does uses the web.config, I have only used it with ASP.Net/Web Matrix applications.
With PHP, it has it own .ini file that is used etc. And I have never used a web.config file for classical ASP.
That is not to say that I don't need one now ! LOL
That being so, I will most certainly see what happens after I  examine/verifying and see if it resolves the issue.

 Vitor -
   A most helpful link and article. It has clarified some items that I have wondered about and has increased my understanding with SMB.
I have always seemed to at times struggle with roles, permissions and authentication !
For both of you -
 Although the coding for the path in both types of application, classical ASP and PHP were initially reviewed, I think the problem was clouded by minor issues that create one big issue. Those minor issues have been resolved.
Revisiting the code for the construction of the path,  uses variables based on user,  has resulted in changes to the coding of the path.
And as a result, now allows the PHP application to successfully connect,  every time,  to the data storage server.
I have yet to change the ASP coding.
Why it worked before ? I have no clue - I only know that it did, something changed and set off a chain reaction - lol.
But bad things happen for a good reason.
I will post later today or tomorrow with the results of the ASP changes.
Thank you both and until then...
dogsareitAuthor Commented:
Okay, this was the solution:

1. recoded the UNC path
2.remapped drives to data storage server
3.reboot all servers

I am splitting the points between David and Vitor since both gave me food for thought.
If this is not agreeable, pls contact me.
I thank you both for responding and for your input - it was appreciated.

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dogsareitAuthor Commented:
Okay, this was the solution:

 1. recoded the UNC path
 2.remapped drives to data storage server
 3.reboot all servers
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Microsoft SQL Server 2008

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