Using the local jobs directory when deploying services across multiple computers
The jobs directory is where the output of your service is written so that clients can retrieve the results of a geoprocessing task. If your ArcGIS Server configuration has multiple computers, the jobs directory must be a location accessible by all computers that host the service. This means that you will use a UNC path to this shared location. However, writing output across your LAN is slow compared to writing data to a local disk. To make more efficient services, you want to check the Local Jobs Directory option found in the service properties directory.
Using local job directories will significantly improve performance with SOCs on multiple machines.
When the Local Jobs Directory option is checked, your service will write output to a jobs directory on the disk drive of the SOC machine. This local jobs directory is the same as the ArcGISSOC account temporary directory (typically C:\Documents and Settings\ArcGISSOC\Local Settings\Temp or C:\Users\ArcGISSOC\AppData\Local\Temp, depending on your operating system). When your service has finished executing, ArcGIS Server moves the contents of the local jobs directory to the shared jobs directory (the UNC path specified for the Jobs Directory property) so that clients can access the results. While the same amount of data is still being moved across the LAN, it is much more efficient for ArcGIS Server to move the contents of the entire local jobs directory once than it is for your service to write many individual files one by one across the LAN to the shared jobs directory.
When geoprocessing services make use of either Spatial Analyst or Coverage tools, you should change the ArcGISSOC account temporary directory to another folder such as C:\arcgisserver\temp. Some of these tools have limitations when writing to a path with more than 100 characters or with spaces. The full path can quickly exceed 100 characters with the directory location, service name, and unique job ID combined.