Can compressing Program Files save space *and* give a significant boost to SSD performance?

Question

Considering solid-state disk space is still an expensive resource, compressing large folders has appeal. Thanks to VirtualStore, could Program Files be a case where it might even improve performance?

Background

In particular I have been reading:

SSD and NTFS Compression Speed Increase?
Does NTFS compression slow SSD/flash performance?
Will somebody benchmark whole disk compression (HD,SSD) please? (may have to scroll up)

The first link is particularly dreamy, but maybe head a little too far in the clouds.

The third link has this sexy semi-log graph (logarithmic scale!).

Quote (with notes):

Using highly compressable data (IOmeter), you get at most a 30x performance increase [for reads], and at least a 49x performance DECREASE [for writes].

Assuming I interpreted and clarified that sentence correctly, this single user's benchmark has me incredibly interested. Although write performance tanks wretchedly, read performance still soars. It gave me an idea.

Idea: VirtualStore

It so happens that thanks to sanity saving security features introduced in Windows Vista, write access to certain folders such as Program Files is virtualized for non-administrator processes.

Which means, in normal (non-elevated) usage, a program or game's attempt to write data to its install location in Program Files (which is perhaps a poor location) is redirected to %UserProfile%\AppData\Local\VirtualStore, somewhere entirely different.

Thus, to my understanding, writes to Program Files should primarily only occur when installing an application. This makes compressing it not only a huge source of space gain, but also a potential candidate for performance gain.

Is this accurate? Will compressing Program Files provide a significant read performance improvement with only a negligible write performance degradation thanks to VirtualStore?

I've postponed my own testing of Program Files directly due to confusion from the beginning of this post which suggests turning compression off may not immediately decompress the files (though I intend to use the compact command which may).

Answer 1

There is a flaw in your line of thinking.

Thus, to my understanding, writes to Program Files should primarily only occur when installing an application. This makes compressing it not only a huge source of space gain, but also a potential candidate for performance gain.

Virtual Store is not used if the program is running as Admin. In the case of Setup Programs, this is all setup programs.

It's very rare to run into a program that isn't UAC aware these days and where VirtualStore takes over. For example, my Virtual Store only lists Foxit Reader.

Compressing it though, does look interesting. In my case, compressed my Program Files out of curiosity. My most disk intensive programs is the Total War series: Napoleon, Empire, Shogun 2. In particular, switching between Battle map and the Campaign map involves a heavy amount of reads.

I decided to compress the Steam folder and fire it up a few times. Predictable, since the game loads require heavy sequential reads, it was slower. My map loading times went from 38 seconds to about 48, although it actually took over two minutes my first time loading.

I haven't tried other applications.

Answer 2

It will depend on your system. Compact command is fast, but not compress files so good. Average read speed is known and average decompression speed also can be calculated. But I don't think that there is possible significant improvements. At least it's not so good for single core processor.

There is a dilemma:

[load time of uncompressed data]

vs

[load time of compressed data]+[decompression time] (higher memory usage in as the side effect)

loading time from ssd is about 150-200mb/sec, decompression speed is about 20mb/sec. So, usual compression raito should be more than 10x and it doesn't looks like a real thing.