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Evaluating Performance

We tested network I/O performance using both emulated I/O and various traffic/assault tests (see How we did it) and found Windows 2008 Server performance has improved -- and especially improved when Vista is the client.

Microsoft's new client and server TCP/IP stacks, encompassing both tcpip.sys and the older Winsock API kit, have been updated. The network interaction stack, NDIS, has also been upgraded from Version 5.6 to 6.0. The TCP/IP stack contains native, rather than emulated IPv6 support. Choosing either IPv4 or IPv6 support is an interchangeable action, and management is identical.

The new stacks also have the ability to dynamically respond to communications latency in network connections as they possess the ability to dynamically change TCP packet window size, which allows a communication channel to be more efficiently stuffed with data.

Speed Boost

SMB 2.0, unlike SMB 1, has performance enhancements that are designed to allow greater speed. One of these enhancements allows for larger buffer sizes when both reading and writing files. More open files can also be sustained at a single exercise like a file folder copy, or the number of files open-for-write concurrently.

In our testing we found that under light loads, the effects in terms of speed of tasks like copying folders, streaming media and loading complex Web pages aren't strongly demonstrated, but the effects under heavy loads, however, favors performance for Vista, strongly. Depending on the mixture of I/O (but pronounced under streaming media and heavy file copying), Vista can be as much as 43% faster than Windows XP SP2 in copying operations and 18% faster in opening concurrent streams.

This also means that there's a two-class affinity for clients of Windows 2008 Server Editions -- Vista and everyone else, including Windows XP SP2, MacOS (we used 10.4.10 and 10.5.2) or other SAMBA clients that use SAMBA 3.0.2+ connection methods. If you have a client with the new stack, you're more efficient, and, therefore faster under higher loads, but you're a second-class citizen if your stack isn't up to date.

Vista's Role

Windows Vista supports and is shipped with both SMB 1.0 and SMB 2.0, whereas XP supports only SMB 1.0. Microsoft claims that Vista should be able to obtain better file/folder copy speeds over XP, especially in networks with higher latency. In our lab, higher latency (emulation over Ethernet 10Base-T) or low latency (same network subsegment with Gigabit Ethernet), Vista completed folder copies at least 35% faster, and in one run of tests, 71% faster than Windows XP SP2. As SMB emulation for Apple's MacOS and most Linux clients are based on Samba, which is also based on SMBv1, these clients were tested and, as expected, showed no improvement in speed when connected to Windows 2008 Enterprise Edition over Windows 2003 Enterprise edition on the same hardware.

Windows Server 2008 also supports TCP/IP processing to be offloaded to supported network cards. In such a relationship, the TCP/IP Offloading Engine (TOE) card doesn't interrupt any of the CPUs to service TCP/IP traffic and protocol relationship requests, ostensibly speeding up network throughput.

When we swapped from a Broadcom Gigabit Ethernet network interface card to an Intel TOE Gigabit Ethernet NIC, the speed effects become highly demonstrable -- even for clients that use older SMB and non-Windows TCP/IP communications stacks (such as Macs and Linux clients/servers).

This change cut CPU utilization (as measured by Perfmon) during our TCP SYN distributed DoS assault test from 48% to 18%, and in our TCP connections test from 61% at peak to 16% at peak. While TOE cards have been around for several years, we haven't seen the stark differences in performance from them.

We also assaulted the network side of Windows 2008 and IIS7 with a simple test get/post test that emulates a large number of users with get/post requests via http for delivery of static pages. We were able to increase the number of gets (using two independent Gigabit Ethernet connections concurrently) by 32% on the same hardware with Windows 2008 Server over Windows Server 2003.