Current setup:

 

1x 10TB HGST Parity

7x 10TB HGST Array Devices (xfs)

1x 3TB WD HDD Cache (btrfs)

1x Flash Drive for Boot Device (vfat)

 

All of this is in a Dual Xeon 4u 24bay Supermicro X9DR3-F, running 6.9.0-rc2.

 

I'm over 60tb used of the 70 I have in my array so it's getting time to add new drives. This is scary and I am beginning to have worries over things like drive failures/redundancies, but that's a different question. 

 

Over the years I've read conflicting things about cache drives (SSD/HDD) and would like to know the current best practices. I'm planning on adding maybe 6 more large drives, and maybe throw in a couple new drives for the cache. Should I get SSDs? High reliability HDDs? Bigger drives?

 

1. I know I need to have another cache drive at least, what drive (or drives) would you recommend adding?

2. Should I have a 2nd parity drive? 

3. I'm using a single flash drive as the boot device, should I add another or is it fine? 

4. Lastly: I worry about losing data. Everything is replaceable, but I know it'll be a pain if a giant drive eats it, anything I can do to allay my worries?

 

BONUS: I've just recently learned about DAS, and there's a kernel of an idea for me to make a dedicated machine with a beefy, modern cpu to handle all the docker/transcoding/compression stuff. My machine currently has dual xeon E5-2680 that were, in their heyday, absolutely beastly, AND it has 256gb ram, but I know a modern AMD chip would probably blow it out of the water. Am I overthinking things? 

Picture of setup in case it's easier to grok.

One more quick followup to the question about worrying I'll lose data:

 

After I posted, I checked a few other posts and saw mention of people using raidz1? Is that the consensus best way to add redundancy to an unraid pool? One of my current big worries is about losing a drive, and if I could make my array have some protection that would be rad. If I added more drives (like, 8x 14tbs or something) could I then have them raided, move my data over, and then reformat the existing array devices to have redundancy? Or is there a better way?