[coreboot] (libre) Add-on cards for getting higher SSD throughput on the KGPE-D16?

[Alberto Bursi]

On 03/01/2018 09:20 PM, Timothy Pearson wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 03/01/2018 01:36 PM, Daniel Kulesz via coreboot wrote:
>> Hi,
>>
>>
>> (3) put in some PCIe SATA3 card => any recommended chips that respect freedom?
> There are very few.  You can try some of the Marvell devices but you
> will still be limited by the host side bus as these old Opterons only
> support PCIe v2.
>

Marvell and Asmedia controllers on sata cards are kinda garbage, many 
quirks.

Neither respects freedom anyway but a SAS controller crossflashed to IT 
(dumb) mode (so that it does not have any RAID capability) is the most 
reliable way to add Sata ports to a board, as SAS is retrocompatible 
with Sata, and SAS controllers have an entirely different level of 
quality (both hardware and drivers).

>> (4) get a m.2 SSD instead together with some PCIe adapter => the cards don't have a co-processor, right?
> Yes, they do.  NVMe devices have an integrated proprietary controller to
> manage data storage / wear levelling.

If we go that way, also mechanical hard drives, USB flash drives and 
pretty much any storage device showing up as "block device" has a 
storage controller running a proprietary firmware.

SSD firmware is more complex and their controllers are very beefy and 
usually multicore because of performance though.

>> (5) stay with SATA2 and live with the limited speed
>>
>> Any recommendations for a freedom-respecting choice?
>

Sata2 speed limitation is less bad than it might sound. What matters 
most for system responsiveness is the transfer speed on random 
read/writes, which is NOT anywhere near Sata 2 speed cap, more like 
20-50MB/s at most on very fast SSDs. Just look up SSD benchmarks for 
actual stats.

The high speed numbers on SSDs are for sequential transfers, for example 
when you copy over a relatively large file, and that will hit the Sata 2 
speed limitation.

-Alberto