RAID 0 configuration cache question

[huangcck]

Hi!

I decided to upgrade my dad's HP Envy 15 Bang & Olufsen with a SSD "in addition" to his HDD.

It's easy enough because HP already have the whole thing set up with RAID/Intel RST, just needed to buy the right one and plug it in. Originally I just wanted to put in a 32GB or 64GB M.2 2280 SATA as a RAID 0 acceleration cache. However, I couldn't really find a new one of those sizes as they are all out of stock. It's not surprising because the demand for them is low. The smallest one is 128GB and it cost $30 for a generic China brand.

Luck would have it, I actually found on Newegg a Mushkin Enhanced Helix-L M.2 2280 250GB PCIe Gen3 x4 NVMe 1.3 3D TLC for $7 more. Yes, it so happened my dad's Envy supports NVMe and I read it is insanely faster in comparison to the M.2 2280 SATA.

So I have a few simple questions, which again for some reason just couldn't find through google searches. If you could answer them, greatly appreciate it.

But before asking, please do not suggest that I put the OS on the SSD. My father would not allow me to do that. He's old and barely agreed to let me install this for him because he doesn't like the hassle. I'm just going to plug it in, set up the RST and just let it be. This is also the reason he won't simply let me replace the 5400 rpm HDD with a 2.5" SSD. Thank you.

1) This is just for my own curiosity. Since the NVMe is so much faster than SATA, does this mean it will also be faster than whatever 2.5" SSD say if I did choose to replace the HDD? I assume because HDD bay uses SATA.

2) So I got most of the information about this from this page (https://www.wepc.com/tips/ssd-cache/), which did a lot of benchmark and testing. Apparently using RAID 0 configuration SSD cache improves the overall performance of the HDD close to a straight up SSD. If that is true then it makes very little difference if programs are installed on the SSD or the cached HDD?

The reason is since this is a 250GB and a max of 64GB can be used as cache, the rest are actually allowed to be partitioned as another drive for standard usage. Now, granted again he doesn't want the hassle of uninstalling all the programs such as Chrome, Firefox, etc... and reinstalling them on the SSD, but according to the test done on that page, it wouldn't even mattered if he did. Correct? Then also future programs he install shouldn't need to be installed on the SSD either.

3) What is the "size" of the cache I should set on the RST? Should I max it at 64GB? I read that is redundant as you don't need more than 30GB, the rest beyond that will yield very small improvements. I read that for each GB you set, it uses a certain amount of RAM also. However, I could not find any information on how much RAM it uses per GB cache. How much RAM is used per GB cache? I mean if it is a few hundred MB, who cares, but if it is going to run up GB of RAM, then I rather not despite my dad has 16GB of RAM. He... opens a lot of programs and never closes them so probably best to leave him a lot of RAM. 

4) So right now I'm kinda leaning towards 50GB of cache through RAID 0 RST, leaving 200GB space. From the above information, my question is, what is the best usage for this extra space? He's not a gamer, so he doesn't need it for gaming. Since programs can stay on the HDD, and honestly he has very few programs. His whole usage on the 750GB HDD is only 150GB including the OS. I had thought of just telling him to put his data etc... on the SSD and use the HDD as a backup.

Now I read that SSD do not like writing, but new technology has really improved this that typically if you write 50GB per day, it will last 12 years. Most people will not use that much writing per day. Even so, avoid putting things like pagefile, browser temp files, etc... on SSD. However, he also likes making music videos, photoshop works, etc... would it be ok to put those work on the SSD and would it improve the speed? Specifically video rendering? And would it damage the SSD?

Anyways, sorry about all the questions and details. It is more of a learning thing for me as well, I love learning new things. Thanks if you could contribute.