My new laptop has a 750GB 7200 RPM Scorpio Black drive that will be used as a second drive. It is cached via Intel's Smart Drive Technology via a dedicated 32GB mSata solid state cache. There is a seperate 256GB SSD that I use as a boot drive. I'd like to get a TB of storage and have a 1TB 5400 RPM Scorpio Blue drive available to replace the 7200 RPM drive. My thoughts are that since this drive will be cached with the 32GB dedicated cache - the 5400 vs 7200 RPM performance will probably be a non factor? What do you think?
It's still a factor. The little SSD drive still needs to get loaded with information from your HDD. And that information gets loaded as a function of spindle speed, among other things. This is most important when you first load the data into the SSD. Once it's cached there, it should just pull from the SSD.
You don't need a 7200 rpm drive, but it does makes some difference.
First the concept behind the cached HDD, first there was the Seagate hybrid Drive with a very small (8 gig) internal SSD cache), now the separate 32 gig SSD cached HDDs for laptops. The primary intent was to provide a fast boot time and program load as these files would be the most often requested. The 32 gig SSD + HDD comes very close to the performance of a OS + Program SSD with the storage capacity of a HDD.
When a separate SSD for OS + Program coupled with a "cached" HDD, the performance of the HDD becomes very dependent on individual usage, that is do they request load of the same files on the HDD as that is what will be cached. And here in lies the rub, when you request a file from the HDD, It will first check the cache, if not there then go to the HDD. This provides a small performance hit for all files not in cache.
Your question on performance diff between 7200 RPM vs 5400 RPM HDD - No diff for what is loaded in cache, but for all other file request you will take a hit, How much and how noticeable is hard to say.
Bottom line is if you need the extra 250 gigs then go for it, if NOT then I would skip.
I solved the question with my laptop - I went with two 256 gig SSDs. DVDs that I want to watch go on my 64 gig Thumbdrive. Then I also have a external 2.5" 1 TB USB 3 HDD for backup.