[Discuss] ZFS on Raspberry Pi?

[markw at mohawksoft.com (markw at mohawksoft.com)]

You can't make a general argument about a specific example. I have an 8
core AMD FX with 16G ram. It isn't running ZFS, but it is running an MD
RAID5 with 5 4T SCI disks.

I'm running 5 VMs on it: a database VM, a mail server, a web server, a
webproxy/firewall, and a dev server. The machine is down in the basement
in a rack. I have a RP4 running PiKVM in case I need to do something to
the host, I generally don't have to because all access to the VMs is
either through SSH or if there is system issue, the console over
virt-manager.

Its not redundant, but it is old and cheap, and I back it up frequently.
The system itself is not exposed to the internet, but the VM's themselves
are exposed through a Macvtap bridge.

If I wanted to make a redundent version of it, I'd get another system,
replicate the VM storage and setup DRBD between the luns and use
KVM/corosync or something to detect failure (or just do manual fail-over)

The problem of redundancy is kind of a non-sequiteur for a discussion of
VMs. Anything you can do with hardware you can do with a VM, I don't
understand why you think it introduces any new difficulty to the problem.
The VM makes a server just another application.


> On Fri, 29 Jul 2022 10:06:03 -0400
> markw at mohawksoft.com wrote:
>
>> High availability is a fairly specialized deployment and that is
>> accomplished with many different strategies. KVM has provisions for
>> redundant high availability. You can create two servers that have
>> access to the same LUNs (or us something like drbd)
>
> But as I said: you can't do this with a single VM host.
>
> When you start expanding your virtualization infrastructure you can
> rack up some very high initial costs. Let's say for example you have an
> old machine with 4 cores and 8GB RAM which I think is reasonable given
> your previous suggestion. And lets say you want 4 VMs with 2 cores and
> 2GB each (equivalent to a smallish Pi4). Well, you can't fit them all
> on just that one host so you need two hosts. But you still don't have
> HA because if one VM server fails, or is restarted for routine
> maintenance, you don't have enough capacity for all of your VMs so you
> really need at least three VM servers to provide sufficient capacity
> and fault tolerance.
>
> Maybe these costs are worth it (as they certainly are for my employer)
> but for a private network? A Pi cluster may be a better and more cost
> effective solution than virtualization. And the Pi cluster is probably
> the more fun project.
>
> YMMV.
>
> --
> \m/ (--) \m/
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