At last Monday's meeting there was mention of a need to start testing
with NVMe. I volunteered to get some and help with that. Part of my
motivation was the desire to become familiar with it and see if it's
something I might have an application for. NVMe seems to have been
created created mostly for servers and a few other applications that
need extremely fast data access and flow from "disk". From what I've
seen the newer 19" rack servers offer a NVMe slot on the board.
One thing that seems rather puzzling is that NVMe is offered in three
different connection configurations. PCI-E, USB (with a USB connector),
and SSD via SATA (with an SATA connector. Since multichannel PCI-E is
very much faster that either USB or SATA I don't really understand why
the USB and SATA options are offered. It seems a bit like having a car
that's designed and built for racing and only driving it on city streets.
From the various conversations with the test folks over time, it seems
many in the group test on laptops. Many of the newer lap tops have a
connector on the motherboard that connects an NVMe to PCI-E. This and
the above leads me to believe that the testing we want to do is with
NVMe on PCI-E. That's what I'm planning at this time.
I have only desktops none of the ones I support have such a slot on the
mother board. No worries; There are PCI-E adapter boards that NVMe
modules can be plugged into then the board plugs into a standard PCI-E
four channel slot. This is the route I'm planning to go.
The complication is that there are different kinds of NVMe modules and
the PCI-E boards have different configurations as well. At this point I
think I will get a board for "M.2" modules and a module to go with it.
There are still some points I want to investigate before I go ahead. I
want read some of the module data sheets in detail to see if there are
any GotYas that need to be considered. Also I want to see what the "raw"
formatting of the module looks like and if it changes from brand to
brand or with module capacity. My observation has been that
manufacturers always want a "competitive advantage" and sometimes those
"advantages" can turn into "let the buyer beware".
In regard to actual procurement. Many of the modules require heat
sinking most of the adapter boards provide at least some minimal
provision for adding a heat sink. Others come complete with all required
hardware for heat sinking. This gets a bit tricky. The modules provide
the specifications necessary to calculate temperature rise from modules
heat dissipating surface. I still need to find an adapter card with the
corresponding specifications. so a complete thermal analysis can be done.
A final point of interest is that there are some NVMe modules that are
being called SATA instead of just being called NVMe. I would be think
that pretending to be an SATA-SSD drive would just a superficial matter
the desktop would handle and the highs peed data access and flow would
be handled in a very light weight protocol in the kernel. This is just a
guess, but I would think that using the SATA protocol would slow things
down. Since NVMes apparently exist for applications with a huge need to
speed I guess I don't understand this.
Any comments or suggestions are always welcome
Stay Safe and Well!
Pat (tablepc)
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