Re: M.2 storage expansion for RPI 4 (and maybe other boards)

On Jul 31, 2024, at 07:18, Steve O'Hara-Smith <[email protected]> wrote:

> On Wed, 31 Jul 2024 13:39:48 +0100
> Nuno Teixeira <[email protected]> wrote:
> 
>> Hello all,
>> 
>> From bsdnow I've read about a M.2 expansion board that I'm looking for.
>> ( https://www.bsdnow.tv/569?utm_source=bsdweekly )
>> 
>> The board is https://geekworm.com/products/x862 that it is compatible with
>> M.2 NGFF SATA SSDs only, not compatible with NVMe M.2 SSDs, so disk should
>> be choosed carefully.
> 
> M2 SATA is just SATA in a different package it is no faster than
> any other SATA drive and seems to be on the way out. It was mostly about
> making laptop drives smaller. I would avoid it IIWY.
> 
> M2 NVME over PCI-e OTOH is capable of blisteringly fast speeds, the
> PCI-e 3 ones serving my /home mirror hit nearly 3GB/s and they're
> considered slow ones - fast ones claim over 7GB/s (yes bytes not bits).
> 
>> Currently using a USB3 external SSD disk, should I expect a great
>> performance improvement?
> 
> Probably not with M2-SATA - USB-3 is pretty quick. M2 NVME OTOH
> will beat anything else by a very healthy margin. Things to watch for 
> 
> - PCI-e level and number of lanes needed - make sure the latter matches your
> slots. The speed will be determined by the lowest PCI-e level and the
> number of lanes. Most M2-NVME drives require four lanes.
> - Four slot M2 NVME PCI-e x16 cards usually require a sixteen lane slot with
> bifurcation support to four sets of four lanes. The ones that don't cram
> everything down four lanes.
> - Some M2 slots on motherboards are only single lane - it seems strange to
> think of 7-800MB/s as slow but that's how it struck me when I met one.

The specified system context was "RPI 4" as the primary example.
RPi4B's do not have PCI-e slots.


===
Mark Millard
marklmi at yahoo.com