SSD for cache is worth it?

[rgmarks]

Hello guys, i have a 2tb hdd for storage, a 120gb ssd for windows, i now i bought a 500gb evo 850 for games, to get those better loading times. I just got to know a bit of the intel smart response and was wondering, its worth it? Its too much trouble to set up? How much space should i put for cache? Its going to benefit my games on the HDD? thanks!

 

[Solandri]

I believe Intel SRT is limited to a 64GB partition for a SSD cache. But from the testing I did (I played around with different cache sizes on a Thinkpad with a 16GB cache SSD), 8 GB will get you about 90% of all the performance improvement you can expect. Beyond 8 GB, unless you've got a large variety of often-used small files on the HDD, additional SSD cache isn't very useful. The thing you have to understand is that HDDs aren't much slower than SSDs at sequential reads - about 125 MB/s vs 500 MB/s. So only 4x faster. In contrast, small file reads on a HDD frequently are below 1 MB/s. On a SSD they usually hit 30 MB/s, and can exceed 200 MB/s if you're reading multiple small files so they can be queued. So the SSD is tens or hundreds of times faster at small file reads than a HDD. Consequently, SSD caches are designed to concentrate on caching small files. And 8 GB can cache a *lot* of small files.

Is it worth it? It depends on what kind of data you store on it. If you have a bunch of large files (e.g. movies), then you're not going to notice much if any speedup. Either the SSD won't cache the movies (because it's not a small file), or it'll cache them one at a time, making the cache pretty useless unless you're watching the same movie twice. But if you're storing lots of small files on the HDD (like games), the SSD cache can help speed it up considerably. On the Thinkpad I played around with, an 8 GB cache was sufficient to drop Windows' boot time from a minute to just 15 seconds, which is about the same as booting off a SSD. So you can see why nearly all hybrid HDDs have standardized on having just 8 GB of flash cache.

The cache won't help with write speed - those will proceed at the same speed as a HDD. So any drive which you'll be writing to often will be better off with a dedicated SSD instead of a cache SSD.