My setup:

 

Array Devices:

1 x Parity HDD (6TB)

5 x Data HDDs (6TB x 3 + 3TB x 2)

2 x Data SDD ( 525GB x 2) (is this a bad idea?)

Cache Devices:

3 x SSDs (250GB x 3)

 

My Thought Process:

1: Array HDDs are used for all my Documents, Media, and Software (isos, and installation files)

2: Array SSDs are used for vm disks, and docker files.

3: Cache used to speed up copying. (is this what the cache is used for?)

 

Shares:

  Documents, Media, and Software (isos, and installation files) shares: Exclude 2 SSDs

  Vm disks, and docker files shares: Use only 2 SSDs

 

Reading through posts, I can see that there are questions regarding SSDs in an array.

 

Please let me know if this is a good way of splitting my storage.

 

Thanks in advance.

I have no problem with SSDs as data devices, I use them myself for some data because of the high read speed and low power use, but for VMs I'd recommend setting them as unassigned devices or write speed will be much lower. For docker use the cache pool (or an unassigned device).

As Johnnie noted, using SSDs for storage devices is okay; BUT if you're using them for applications that will be doing frequent writes, the writes will be limited by the speed of the parity drive (in addition to requiring 4 I/O's per write) => so using them as unassigned devices is a better idea.  You can back them up to the array periodically; but the normal operation won't have the limitations of array write speeds.

 

Note that 3x250GB cache pool as default raid1 will give 375GB storage.

 

btrfs disk usage calculator

Thanks so much for the advice... will have to remove the SSDs from the array ... looks complicated.

 

The reason I did not do unassigned before was 2 fold:

  - did not realize the performance hit

  - multiple drives, meaning I have to manage the directories across 2 separate mount point? Anything I can do to change this?

A bit of "out of the box" thinking r.e. how to eliminate the performance hit while still leaving the SSDs in the array ...

 

[Note:  I have NOT tried this, but it certainly SHOULD work as long as you get the 2 spanned drives for parity in the right order, so the "SSD part" is matching your SSDs]

 

(1)  Create a parity "drive" using a 525GB SSD and your current 6TB parity drive spanned ("BIG" setting) using this:

https://www.amazon.com/StarTech-com-Internal-Connector-Controller-S322SAT3R/dp/B00M77UNDI

This would give you a 6.525TB parity "drive", where the first 525GB was physically on an SSD.

 

(2)  Now the first 525GB of writes to any disk in the array will be using the SSD part of your parity "drive" => so if you have 525GB SSDs in the array, there won't be use of the 6TB spinner for the associated parity writes.