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Date:      Wed, 31 Jul 2024 07:36:32 -0700
From:      Mark Millard <marklmi@yahoo.com>
To:        Steve O'Hara-Smith <steve@sohara.org>
Cc:        Nuno Teixeira <eduardo@freebsd.org>, FreeBSD ARM List <freebsd-arm@freebsd.org>
Subject:   Re: M.2 storage expansion for RPI 4 (and maybe other boards)
Message-ID:  <147B31D2-D2B4-47B6-B62B-A391AF9C6421@yahoo.com>
In-Reply-To: <20240731151801.9e00f0eeae06979a2d11a93d@sohara.org>
References:  <CAFDf7U%2BEyTF_GWzhgHRGJ58LsJXXd%2BWEnj9zVZF1a20X49yXaQ@mail.gmail.com> <20240731151801.9e00f0eeae06979a2d11a93d@sohara.org>

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On Jul 31, 2024, at 07:18, Steve O'Hara-Smith <steve@sohara.org> wrote:

> On Wed, 31 Jul 2024 13:39:48 +0100
> Nuno Teixeira <eduardo@freebsd.org> wrote:
>=20
>> Hello all,
>>=20
>> =46rom bsdnow I've read about a M.2 expansion board that I'm looking =
for.
>> ( https://www.bsdnow.tv/569?utm_source=3Dbsdweekly )
>>=20
>> 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.
>=20
> 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.
>=20
> 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).
>=20
>> Currently using a USB3 external SSD disk, should I expect a great
>> performance improvement?
>=20
> 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=20=

>=20
> - 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.


=3D=3D=3D
Mark Millard
marklmi at yahoo.com




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