From the "Performance Tuning Guidelines for Windows Server 2008":
The default is 0. This parameter disables the processing of write flush commands from clients. If the value of this entry is 1, the server performance and client latency for power-protected servers can improve. Workloads that resemble the NetBench file server benchmark benefit from this behavior.
The default is 512. This parameter limits the number of concurrent “asynchronous” SMB commands that are allowed on a single connection. Some file clients such as IIS servers require a large amount of concurrency, with file change notification requests in particular. The value of this entry can be increased to support these clients.
Smb2CreditsMin and Smb2CreditsMax
The defaults are 64 and 1024, respectively. These parameters allow the
server to throttle client operation concurrency dynamically within the
specified boundaries. Some clients might achieve increased throughput
with higher concurrency limits. One example is file copy over
high-bandwidth, high-latency links.
The default is 0, which means that no additional critical kernel
worker threads are added to the default number. This value affects the
number of threads that the file system cache uses for read-ahead and
write-behind requests. Raising this value can allow for more queued
I/O in the storage subsystem and can improve I/O performance,
particularly on systems with many processors and powerful storage
The default is 0. This setting is available starting with Windows
Server 2008 SP2. By default, the SMB redirector throttles throughput
across high-latency network connections in some cases to avoid
network-related timeouts. Setting this registry value to 1 disables
this throttling, enabling higher file transfer throughput over
high-latency network connections.