Monday, February 04, 2008

Details on the File Copy Improvements in Vista SP1

Mark's Blog - Inside Vista SP1 File Copy Improvements

"Windows Vista SP1 includes a number of enhancements over the original Vista release in the areas of application compatibility, device support, power management, security and reliability. You can see a detailed list of the changes in the Notable Changes in Windows Vista Service Pack 1 whitepaper that you can download here. One of the improvements highlighted in the document is the increased performance of file copying for multiple scenarios, including local copies on the same disk, copying files from remote non-Windows Vista systems, and copying files between SP1 systems. How were these gains achieved? The answer is a complex one and lies in the changes to the file copy engine between Windows XP and Vista and further changes in SP1. Everyone copies files, so I thought it would be worth taking a break from the “Case of…” posts and dive deep into the evolution of the copy engine to show how SP1 improves its performance.

Copying a file seems like a relatively straightforward operation: open the source file, create the destination, and then read from the source and write to the destination. In reality, however, the performance of copying files is measured along the dimensions of accurate progress indication, CPU usage, memory usage, and throughput. In general, optimizing one area causes degradation in others. Further, there is semantic information not available to copy engines that could help them make better tradeoffs. For example, if they knew that you weren’t planning on accessing the target of the copy operation they could avoid caching the file’s data in memory, but if it knew that the file was going to be immediately consumed by another application, or in the case of a file server, client systems sharing the files, it would aggressively cache the data on the destination system.

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Mark provides a low level, detailed view into file copying, Vista and SP1.

If you ever wondered what's going on under the covers when you copy a file on Vista, this is a must read.

2 comments:

Anonymous said...

The Vista file copy has got to be the most frustrating and annoying part of Vista, especially over a network. How many times have I stared at the thing saying "0%... Calculating Time Remaining" and it just sits there. Horrible, horrible, horrible, how could they screw this up this badly?

Greg said...

Based on Mark's post it seems MS heard our screams loud and clear and are trying to address them in SP1.

As a software developer I have to say I've been there, done that, built a system that seemed good at the time, but in hind sight I had to wonder just what the heck I was thinking...

I DO wish that SP1 hadn't taken a year to get out. It probably had to release in sync with Win2k8, since there's shared tech in both. But that could have been Vista SP2?

Anyway, we'll be able to get our hands on Vista Sp1 in a month or so (I read that it will be released for download mid March?)...