The idea behind ReadyBoost is that you can plug in a USB flash drive and make your computer a little faster. You really shouldn’t obsess on it. After all, any performance gains you realize will quickly be lost if you spend hours analyzing whether it’s working or not.

But if you’re obsessive like me, you can find detailed information about ReadyBoost performance in Event Viewer (which you can find in the Computer Management console), at the following location:

Event Viewer \ Applications and Services Logs \ Microsoft \ Windows \ ReadyBoost \ Operational

In particular, look for Event ID 1015, which provides detailed performance information. For example:

Summary of ReadyBoot Performance:
Io Read Count: 18190
Io Read KB: 384754
Cache Hit Count: 11388
Cache Hit KB: 201324
Cache Hit Percentage: 62.60582737768
Cache Fragmentation: 9.39796981101432
Compressed Data Size KB: 305942
Raw Data Size KB: 494500
Compression Ratio: 1.61631679155397
Cache Size KB: 386515
Boot Prefetch Time us: 44573374
Boot Prefetch Bytes Read: 365203456
Boot Timestamp (UTC): 1/1/2007 7:56:05 PM
Last Boot Plan Timestamp (UTC): 1/1/2007 7:21:15 PM
Last Boot Plan Timestamp (Local): Mon, Jan 01 07, 02:26:07 PM

Interesting stuff, even though it doesn’t tell you exactly how much performance gain you get. Note the Cache Size KB line, which indicates how much of your total cache is actually being used. I have about 800 MB allocated, but less than 400 MB is actually in use. I guess this helps to answer the question of how much you need–500 MB is probably fine.

Event IDs 1011 and 1014 will tell you whether ReadyBoost caching is enabled for each of your hard disks, as the following demonstrates:

Caching was enabled for device (\Device\HarddiskVolume3).

Caching was disabled for device (\Device\HarddiskVolume3).

If you know of another way to get more detailed information about ReadyBoost performance, please add a comment.