Intel Smart Response Technology implements storage I/O caching to provide users with faster response times like system boot and application startup. On a system with [A] traditional HDD, performance of these operations are limited by the HDD, particularly when there may be other I/O intensive background activities running simultaneously like system updates or virus scans. I/O caching accelerates system response by putting frequently used blocks of disk data on an SSD, which provides dramatically faster access to user data than an HDD. The user sees the full capacity of the HDD with the traditional single drive letter (i.e. C:) with the system responsiveness similar to an SSD.
In essence, it works like this. If you boot your computer often then the smart portion of the technology will tell the system to cache your boot up files. The first time you boot your system the files will not be cached, so startup will occur from the standard HDD. The second time you boot your system the files will be cached and startup will occur faster.
The same is true for your applications. If you run Photoshop often, the long launch sequence is stored on the SSD. Files like ISOs, music and such on the other hand are not cached on the SSD, another part of the smart side of the technology.
One issue we've observed in the lab is that all of this caching takes up space on the SSD. With Intel only releasing 20GB models, the available space tends to fill up quickly if you launch several different programs. The technology is always trying to cache your frequently used data, so what may have been cached two days ago may not be cached when you want to use it today if you've launched several other programs in between. At this time SRT is limited to just 64GB of caching space, even if you want to use a 120GB drive. The spare area is given another drive letter if you choose to use it. This can be a positive in some cases or a negative in others.
If you happen to have a 120GB OCZ Vertex 2 SSD with a SandForce SF-1200 controller capable of reading 285MB/s and writing 275MB/s, then limiting the drive to just 64GB of capacity for the cache is a good thing. This will allow the drive to reserve the spare area for background work and keep the drive running faster than if it was filled. We believe Intel used some type of real time compression with the IO cache algorithm, but were never able to verify that claim with Intel.
To further complicate Intel Smart Response Technology, two modes are offered. The first is Enhanced Mode, a read only cache mode that uses up to 64GB of space to cache files that can be read back quickly. The second mode is Maximized Mode, a mixed read / write cache system that allows the SSD to cache system writes and later transfers the data written to the SSD to the HDD. In Maximum Mode you gain the ability to write data to the SSD so it happens quicker, but you also use space that was once reserved for reading back cached data.