Is there an advantage in using M.2 SATA drives as Cache?

[wayner]

I am looking at building a new unRAID server and I see that some new motherboards come with two M.2 slots.  Would it make sense to get such a board and to use both slots as cache drives, giving redundancy for cache drives?  I would think that using M.2 drives as a cache would give a faster system than using typical SATA SSDs as a cache drive, would it not? 

 

I store my appdata share on my Cache drive which presumably helps some of the dockers run faster, such as retrieving Fanart for SageTV.

[trurl]

Sounds good.

 

11 minutes ago, wayner said:

my appdata share on my Cache drive which presumably helps some of the dockers run faster

In addition to appdata, domains and system shares should be on cache so dockers/VMs won't have performance affected by slower parity, and so array disks can spindown since these shares always have open files.

[wayner]

Thanks - I just found a Space Invader video that does an excellent job explaining this.  

 

What size would be enough for 3-4 VMs and 20 or so dockers.  Would 256GB be enough or would you want to go larger? (edit - I mean 256GB for each of the two M.2 NVME SSDs)

 

And what is your opinion on having two disks serving as the cache to have redundancies.

Edited December 9, 2021 by wayner

[WETAFROMAN]

Redundancy is always a good idea. If you can afford it do it.

 

As for the size. There are more factors that have to be considered for this. Some OSs take more space then others. i.e. pure Linux is much smaller then Windows 10 or MacOS. Same with Dockers some containers are larger then others. It is really a case by case basis. Also you have to consider will there be anything else in the future that you want to run off of those NVME drives and do you need to assign space to a share or make your VM drive pool larger to accommodate that?

 

Personally I would say buy a 1TB unit. They are super cheap now, especially if you buy 3.0 instead of 4.0.