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Vista SP1 will deliver big network speed boost


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ZDnet article

I downloaded the release candidate of Vista Service Pack 1 yesterday and was prepared to wait till its public debut next week before writing about it. But after upgrading a few machines here and doing some tests, I changed my mind. If Microsoft’s decision to ditch the WGA kill switch in SP1 didn’t convince you, would you be interested in a 300% increase in network file transfer speeds?


Forget the reports you might have read about SP1 resulting in no performance boost. That story was based on a silly artificial benchmark involving scripting of Office applications. Back here in the real world, where gigabit network connections are now commonplace, you’ll see at least one huge improvement when transferring files over network connections.


In its original release, Vista had some design problems with its networking stack, resulting in slow file transfers, especially when connecting to computers running Windows XP, Windows Server 2003, or Windows Home Server (all three of these products share a great deal of their code base, including core networking components). In Vista SP1, file transfer speeds are dramatically improved. In this post, I’ll describe what I saw.


I did two sets of file-transfer tests using two separate systems configured to dual boot between Vista RTM and the new Vista SP1 release candidate. Both systems have dual- or quad-core processors (both in the Intel Core 2 Duo family) The first group of files consisted of two large DVD images in ISO format, totaling 4.2 GB. The second group of files was a folder filled with more than 3,000 files of all types, in 299 subfolders, totaling roughly 6.5 GB.


For the first test, I transferred the two groups of files from a shared folder on an HP MediaSmart Windows Home Server to the two test systems running Windows Vista RTM, recording the total transfer time for each one. Then I rebooted the two systems into an SP1 installation and repeated the test. I converted the times into throughput rates; here’s the result (note that bigger bars equal higher throughput and thus better performance):



Throughput for file transfer from Windows Home Server


As you can see, the file transfers under Vista SP1 were dramatically faster than the Vista RTM times. For the directory full of many small files, the performance increase was more than 300%; for the large files, the speed increase was roughly 260%. Note that you can expect similar results when transferring files from Vista to systems running Windows XP or Windows Server 2003.


For the second set of tests, I performed transfers between the two machines running equivalent versions of Windows Vista: RTM to RTM, SP1 to SP1. Here, the results were less dramatic. For the folder full of small files, the throughput rate increased by about 50% under SP1, and the large files transferred slightly slower, although still faster than the transfer from Windows Home Server.


File transfer between machines running Windows Vista


When I spoke with Microsoft about this phenomenon a few months ago, they explained that the issue was caused by a design change in Vista that eliminated the buffering used by XP and its siblings when transferring files over a network. Bypassing the cache read-aheads and deferred writes makes for better disk-to-disk performance and provides better control over how much data you’re pushing over the network, but the mismatch slowed down transfer speeds in Vista RTM. That’s been addressed effectively in SP1, as these results show.


Unfortunately, the other big Vista networking issue doesn’t appear to be addressed in SP1. If you run an application that uses the Multimedia Class Scheduler (such as Windows Media Player), you’ll continue to see a performance hit when transferring files over gigabit network connections. For more details, see this explanation from Microsoft’s Mark Russinovich and earlier test results from ZDNet’s Adrian Kingsley-Hughes.


But when I fired up Windows Media Player while a network file transfer was in operation I saw a sharp drop in throughput when the music began playing and then saw throughput pick back up when WMP was closed.


Even with the “release candidate” label, this is still a beta, so I can’t recommend SP1 yet unless you’re willing to assume the risks that come with beta software. But so far, the results I’m seeing are extremely encouraging.

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