They will name 2π ‘τ’, so we’ve chosen Raspberry Tau for this proof-of-concept.
We’ve connected two Raspberry Pis via their onboard ethernet interfaces (via a switch, so we can simply SSH into them) and booted via 2GB SD cards with a Raspbian image. After upgrading to a kernel that has kernel headers available, we built DRBD® modules and voilá! A Raspberry Tau cluster is born.
We’re replicating the data on the USB-Sticks; their performance nicely matches the available network. Here’s
/proc/drbd (shortened and line-wrapped for readability):
root@raspberry-alice:~# cat /proc/version Linux version 3.2.0-3-rpi (Debian 3.2.21-1+rpi1) ([email protected]) (… Debian 4.6.3-1.1+rpi2)…) root@raspberry-alice:~# cat /proc/drbd version: 8.4.2 (api:1/proto:86-101) GIT-hash: 7ad5f850d711223713d6dcadc3dd48860321070c build by root@raspberry-bob, 2012-09-18 12:58:08 0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r----- ns:805304 nr:0 dw:348628 dr:818596 al:127 bm:70 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:0
As Raspbian is Debian-based, Pacemaker (and Heartbeat resp Corosync) packages are available. Therefore, you can build a cheap, low-power, High-Availability cluster quickly.
Disclaimer: for a real HA-cluster, you’d need a few more things.
- a STONITH device (if power is supplied via a Linux PC, you could turn off the USB port by software), and
- redundant network connectivity (USB ethernet adapter).
Of course, if you’re just clustering your media library, these things might not be mandatory. Precompiled packages are available to our subscription users, but open-source versions are on our GitHub. If you have any questions about Raspberry Tau, contact our team.