Raspbian Jessie w/ external / on btrfs ?

Raspberry Pi 2 fun this weekend!

Quite successfully managed to relocate / to an external disk.  In my case, the external disk is an old 1TB hard drive in one of these snazzy docks (does not pass S.M.A.R.T. data).  Then I tried it with an SSD to see if it was any faster.  It was, but not enough to justify its immigration from my desktop as a cache device.
That’s all well and good, but I’d like to achieve some redundancy.
First, I started with MDADM, that didn’t work.  Then I moved to btrfs.  Seemed promising, but I get a kernel panic during boot.
Guides used:
Will do more fiddling later..

I made a thing

A while back, I got the itch for some retail therapy and bought a 2U, 12-bay Supermicro from the nice folks over at Garland Computers.  Couple of quad E5-somethings, a tooon of RAM, and a bit of capacity in the form of a ZFS array smeared over a mish-mash 1- and 2TB hard drives.  Things were great, until the sound got to me..  and its not a fan I could do anything about; it was the fan inside the hot-swap power supply :(.  It was way more storage than i needed, massive energy hog, and that damn fan.. so it went to being on all the time, to being on most of the time, to not being on at all.

Maybe it was all the stuff about this being the 25th anniversary of Linux and all, I felt the need to redo my desktop.  Initially it was Kubuntu Xenial on the cheapy 240gb SSD..  then I realized how many 1TB drives I had sitting around.  I tore it down and rebuilt it using these fantastic instructions on how to install Ubuntu root on ZFS.

travis@chisburger:~$ sudo zpool status -v
[sudo] password for travis:
 pool: rpool
state: ONLINE
 scan: resilvered 7.89G in 0h3m with 0 errors on Sat Sep  3 11:15:20 2016
config:

       NAME                                              STATE     READ WRITE CKSUM
       rpool                                             ONLINE       0     0     0
         mirror-0                                        ONLINE       0     0     0
           ata-ST31000528AS_5VP05QRD-part1               ONLINE       0     0     0
           ata-ST1000DM003-9YN162_W1D1M3Q0-part1         ONLINE       0     0     0
       cache
         ata-SPCC_Solid_State_Disk_15022293000000000380  ONLINE       0     0     0

errors: No known data errors

travis@chisburger:~$ sudo zpool list -v
NAME   SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT rpool   928G   536G   392G         –    26%    57%  1.00x  ONLINE  –  mirror   928G   536G   392G         –    26%    57%
   ata-ST31000528AS_5VP05QRD-part1      –      –      –         –      –      –
   ata-ST1000DM003-9YN162_W1D1M3Q0-part1      –      –      –         –      –      –
cache      –      –      –         –      –      –
 ata-SPCC_Solid_State_Disk_15022293000000000380   224G  9.70G   214G         –     0%     4%

This is running in a desktop with a 4690k with 20gb of RAM.  I’m very curious to see what effect, over time, that cache device will have on responsiveness.

Through the course of setting this up, one of my 1TB drives failed, and I was able to replace it no problem.  I just needed to remember to run ‘grub-install’ on the new drive.

Hope everyone is having good luck with their projects!