I can't claim this as mine, I feature requested from my OS, and was emailed this solution. I wanted a JBOD cache pool, as this would best leverage my upgrades and I don't need the protection of new btrfs-raid. Been running for two months, so far so good, figured I should share the knowledge.

 

Instructions:

 

0.)     Backup any data you don't want to lose. These steps will format your cache drive(s). You have been warned. ((appdata, DOMAINS, system?))

 

1.a)   If you are adding new drives to your cache pool; add them like normal. This is where your drive will get formatted by web-ui, using default RAID1. 

          If you want to change your existing pool to JBOD, just move to 1.b.   "Okay, People. Nothing to see here! Move along."  -- Officer Barbraide 

1.b)   Navigate to the Main tab in the unRAID web ui, then click on blue link ‘Cache’ next to your first cache device.

2.  )   Locate the Balance Status section.  Next to the ‘Balance’ button there is a empty text box, paste this in there:

  -dconvert=single

3.  )  Click the ‘Balance’ button.  The process may take a while to convert the existing data in the cache pool but you’re free to keep using the server as this runs in the background.

4.  )  Move back your data onto cache pool.

 

Note: note entirely sure, but if one adds another drive onto their pool, I think web-ui (by it's design) will want to format the cache pool. So, safe play would be to backup first. Then again, I haven't tried it, so I don't know with 100% certainty if it will. Unfortunately I don't have a third ssd to try and test it.

 

Thanks to Eric Schultz, and Lime Technology for their time and response to my question.

2 hours ago, Jcloud said:

Note: note entirely sure, but if one adds another drive onto their pool, I think web-ui (by it's design) will want to format the cache pool. So, safe play would be to backup first. Then again, I haven't tried it, so I don't know with 100% certainty if it will. Unfortunately I don't have a third ssd to try and test it.

Since v6.3.3 once the default profile is changed it's maintained when you add a new device, more info and the other available profiles here:

 

https://forums.lime-technology.com/topic/46802-faq-for-unraid-v6/?do=findComment&comment=480421

 

Quote

Since v6.3.3 once the default profile is changed it's maintained when you add a new device, more info and the other available profiles here:

 

Thank you, I wasn't aware -- bookmarking your link for myself. I tried to search before posting, to prevent redundant post/info, I guess I should have tried harder. 

 

Thank you for posting this - it might be what I'm after.  A couple of questions...

 

- Can the drives be of different sizes?

- Do you know if there's a way of deciding which drive a file/folder goes on (or does it just show up as one big drive)?

 

I'm looking at adding a second cache, but would like the opportunity to split a download share and appdata share to separate locations (currently, when a download is unpacking it can hog the disk and mess with Plex transcoding).   I could do this with Unassigned Devices, but this might be another option.

9 minutes ago, Cessquill said:

Can the drives be of different sizes?

Yes, if using the single profile all space will be used.

 

9 minutes ago, Cessquill said:

Do you know if there's a way of deciding which drive a file/folder goes on (or does it just show up as one big drive)?

Not currently, just a big drive

Thank you 

22 hours ago, Cessquill said:

I'm looking at adding a second cache, but would like the opportunity to split a download share and appdata share to separate locations (currently, when a download is unpacking it can hog the disk and mess with Plex transcoding).   I could do this with Unassigned Devices, but this might be another option.

 

I've seen some people in the forums setup their transcode/stream-buffer folder to /tmp/PlexFOO that way it utilizes the ramdrive and is cleared when you reset. Coupled with making a ring-buffer scheme, that might help you out. Assuming you haven't tired that setup yet.

Edit: Found the link I was thinking about, Plex guide to moving transcoding to ram.

Edited December 31, 20178 yr by Jcloud
Found the link I was referencing (more info)

Thanks for that @Jcloud - I've been reading some reports that seem to think you can take down your array if you run out of RAM doing this.  I haven't gone down this route yet, so something to read up on tomorrow.  Thank you.

On 12/31/2017 at 11:59 AM, Cessquill said:

Thanks for that @Jcloud - I've been reading some reports that seem to think you can take down your array if you run out of RAM doing this.  I haven't gone down this route yet, so something to read up on tomorrow. 

 

Well, that's fair, I must admit I haven't touched my DNLA docker (Emby) for a while due to not needing/using it. Good luck.