Rich Freeman via plug on 3 Jan 2022 09:49:06 -0800

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Re: [PLUG] Moving mdadm RAID-5 to a new PC

On Mon, Jan 3, 2022 at 10:38 AM Rich Mingin (PLUG) via plug
<> wrote:
>  The USB controller on the Pis serves *many* masters. I think the ethernet controller is still on it, for example.

This is actually untrue these days with the Pi4.  I would share your
reservations with any previous Pi generation, but the Pi4 has decent
IO - certainly comparable to most cheap SBCs out there.  I don't think
any cheap ARM SBCs have particularly good IO, though some are better
than others and a few have PCIe which helps.

The Pi4 has two USB3 hosts and as far as I'm aware the gigabit
ethernet isn't on either of them.  I get decent performance out of
USB3 hard drives on them.  In theory you could get up to four spinning
disks on one before USB3 becomes a bottleneck but I haven't put that
to the test.

Obviously I wouldn't consider a Pi4 a great option if you need a lot
of IOPS/etc, but for bulk storage it should be fine.  It is my SBC of
choice at this point for lizardfs chunkservers.

I'd love to see a cheap low-power ARM solution with plenty of DDR4+
slots and PCIe lanes, but I don't think anybody makes anything like
that aside from some server-intended hardware that is very expensive.

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