Using m.2 storage as SSD cache?

[CallMeDrJones]

Hi all, I was watching the ULTIMATE Build a Better $1500 Gaming PC Computer "How To" Guide and was interested when Linus said that he planned to dedicate 60GB of the SSD as cache for the HDD to boost performance. I was wondering if a similar thing can be done by dedicating a portion of m.2 storage (say, from a 512GB Samsung 950 Pro) as cache to speed up a SATA SSD JBOD (such as four 2TB Samsung 850 EVO's).

 

If the answer is yes, I have a couple more questions:

• What kind of read/write gains (roughly) might I expect from a setup like this?
• Is there a hardware limit to the amount of m.2 space I can allocate for the cache, and is there a performance "sweet spot" as far as this goes? I don't want to set aside 100GB if it won't be efficient.
• Is there a relationship between the size of the JBOD and the effectiveness of the cache, i.e. will having a larger volume detract from the effectiveness of the cache?

 

Thanks so much!

 

[Shubham Yadav]

The 950 isn't any faster than the 850 EVOs for real world performance because the random I/O isn't that much better. So unless you are looking to boost sequential I/O, you shouldn't even bother trying it.

[Electronics Wizardy]

You can, but there is no reason to. The performance differnce is much smaller.

 

1. Depends on use. The writes will be the full speed of m.2 and any cache file is the full speed. It depends on use and if you use lots of random files of the same files a lot.

 

2. Nope. Your normally doing this in software so you can cache as much as you want.

3. Bigger cache = better, but depends on use.

[CallMeDrJones]

The 950 Pro seems to have a huge advantage over the EVO in terms of average sequential read and write; I'll be doing a fair bit of video rendering and photo/video file transfer, so I do believe increased sequential read & write would be of value to my workflow.

 

http://ssd.userbenchmark.com/Compare/Samsung-950-NVMe-PCIe-M2-512GB-vs-Samsung-850-Evo-500GB/m38554vs3477

 

Any suggestions for how much space to set aside for cache duty? I have no idea how to go about determining this.

[meenmeen1103]

3 minutes ago, CallMeDrJones said:

The 950 Pro seems to have a huge advantage over the EVO in terms of average sequential read and write; I'll be doing a fair bit of video rendering and photo/video file transfer, so I do believe increased sequential read & write would be of value to my workflow.

 

http://ssd.userbenchmark.com/Compare/Samsung-950-NVMe-PCIe-M2-512GB-vs-Samsung-850-Evo-500GB/m38554vs3477

 

Any suggestions for how much space to set aside for cache duty? I have no idea how to go about determining this.

Estimate the average size of files to be transferred and set it to that?