Rich Mingin (PLUG) via plug on 3 Jan 2022 10:49:14 -0800

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

Mostly correct. A few quibbles. OP is on an RPi2. It's not gigabit at all, and the 10/100 is on the USB controller's bus.

Other quibble: On RPi4, there's only one USB controller, a Via VL805. It handles the USB 2.0 and USB 3.0 ports. The power input, despite using a USB-C connector, really isn't USB. It's kind of a braindead power-only USB port, wired to the DC inputs for power management. If you meant something else, show me?

forge@ubuntu-rpi4:~$ sudo lspci
00:00.0 PCI bridge: Broadcom Inc. and subsidiaries Device 2711 (rev 10)
01:00.0 USB controller: VIA Technologies, Inc. VL805 USB 3.0 Host Controller (rev 01)
forge@ubuntu-rpi4:~$ sudo lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Re: ARM with a ton of DDR4 and I/O options: Not yet, but within a year or so, the M1 Mac Minis should be available at reasonable prices, as they get replaced with newer, shinier Apple products. They have a beefy ARMv8A, 8 or 16GB of very fast ram, and tons of wild I/O options. Should be booting Linux on the metal smoothly by then too. Just something to keep in mind. Too expensive to replace most of the low end SBCs, but as a more powerful central point/coordinator, maybe interesting.

Back to OP: If you're tinkering and want to have some more throughput with little to no other changes, then swapping out the Pi2 for a Pi4 should work. I think you can probably even use the existing setup and SD card.

If you'd like to do more involved stuff, I still say a refurb/discarded desktop PC would give massively more performance and options. Depends on what you're planning to do.

On Mon, Jan 3, 2022 at 12:49 PM Rich Freeman <> wrote:
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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