Max limit and performance of SharePoint 2010 Workflow

The max number of workflow running is by default set to 15. This is applicable for both SPD and visual studio workflows.

The number does not include the workflow instances which is 'In progress' state. The number represents the number of active workflows using the processor and it is set for the entire farm and does not depend on the number of front end servers.

The number can be configured using powershell command

Set-SPFarmConfig

More can be read from http://technet.microsoft.com/en-us/library/ff607962(v=office.14).aspx

The existing farm settings can be obtained using the command

Get-SPFarmConfig

Reference <http://technet.microsoft.com/en-us/library/ff607745(v=office.14).aspx>

To know more about SharePoint workflow performance and scalability parameters read the msdn article - http://msdn.microsoft.com/en-us/library/dd441390(office.12).aspx

More about SharePoint 2010 workflow

http://msdn.microsoft.com/en-us/library/hh237664(v=office.14).aspx