Re: Pi5 M.2 HAT

On 10/30/24 23:14, Theo wrote:

Pancho <Pancho.Jones@proton.me> wrote:

On 10/30/24 08:50, Andy Burns wrote:

Pancho wrote:
>

The official NVMe Pi Hat has been out for months,

>
Oh, I don't have a Pi5, and though I kept hearing about 3rd party NVMe
HATs and lack of official one
>

>
OK, I see there is a story about rPi launching actual NVMe M.2 SSDs. As
opposed to a hat. I've no idea why they would do that. The obvious
suspicion is cashing in on a brand name.
>
<https://www.techpowerup.com/328021/raspberry-pi-launches-nvme-m-2-ssds-and-ready-to-use-ssd-kits>

 It may be they are doing it because supply of small-capacity 2230 NVMe is a
bit of a minefield.  eg I checked scan.co.uk and the smallest 2230 they have
is 512GB.  There are some 256GB sold by Amazon.co.uk which are more
expensive (and a few more dispatched by other sellers, of variable
trustworthiness).  At least with the RPi brand you know they're compatible,
and they seem to be decent value.
 

I have three 2242 NVMe, they work fine, apart from some versions of U-Boot boot loader (They actually worked in older versions, then stopped working). A couple of those are 256GB from a couple of years ago, due to the price low differential I would buy 512GB now.
I'm thinking of getting a M.2 NVMe adapter for my rPI5, I'll probably get a Pimoroni one, because it take standard 2280 drives. Best to go with the flow.

It's hard to know what is going on with the Raspberry Pi guys, the
RK3588 devices are clearly faster, lower energy, albeit with shit
software support. Who knows what will happen with the next generation
Arm SoCs. I guess maybe Raspberry Pi have a clue, and hence decided to
monetise the brand now, before a new product wipes the floor with them.

 It'll depend on what fab slots they can get.  Not everyone can fab on the
latest process, especially with a budget.  Also how much cache they can
afford to put on the die.
 RK3588: (64+64+512)*4+(32+32+128)*4+3072 = 6400KiB
RPi5  : 512*4+2048 = 4096KiB
 RK3588 also has 4 extra A55 cores which RPi doesn't have, but is more
expensive ($100+ for the Banana Pi).
 

It's only costs a little more, but the RK3588 is now two years old. For me it it was the first PC quality Pi type device. I think the next generation of Pi type devices may be genuine mass consumer products. The rPi niche is disappearing,  rPi will either become much bigger or much smaller. Saying others have a manufacturing advantage is supporting the idea rPi might have problems in future.
FWIW I'm not a traditional Linux/Unix person. When MS Win NT provided a proper OS, I dropped Unix and was a MS Fanboi for 25 years. I looked at Linux occasionally, but not seriously. Now I think Arm/Linux is about to become a serious mass market desktop PC.
MS seem to be a little nervous too.

I guess I should get one, or maybe an alternative. I just bought a
NVMe USB enclosure which has appalling performance

>
Anyway, is it likely the write speeds are faster than the  read speeds?
I know some enterprise SSDs come in "read mostly" or "write mostly"
flavours, but for a Pi?

 

Dunno, IOPS doesn't mean a lot to me. As TNP says, maybe a write
operation is to cache, and a read is from main memory.
>
On many solid state persistence devices you see a very fast initial
write (presumably to cache) before quickly settling down to a much lower
rate for big files.

 Any decent benchmarking tool should get past the cache to exercise the real
storage.
 

These are marketing benchmarks, about as reliable as VW diesel vehicle emission tests. i.e. They could do it properly, but they don't want to.

I think they've got them around the wrong way.  Their ODM Biwin's 2230 has
more read than write IOPS:
https://droix.co.uk/product/biwin-2230/
>

Yeahbut...
<https://www.scan.co.uk/products/512gb-wd-pc-sn740-m2-2230-pcie-40-x4-nvme-ssd-5000mb-s-read-4000mb-s-write-460k-800k-iops-tcg-pyrite>
650K  IOPS Max. Random Read 4K
800K  IOPS Max. Random Write 4K
But as I said, I don't really understand what IOPS means. The same device quotes a faster Max Read than Max Write (presumably sustained read/write).
I'm not saying the Raspberry Pi NVMe spec is right, just that it is good manners to have a bit more evidence before accusing it of being wrong.

Theo