[gentoo-user] Slightly OT - My new SSD.

[Alan Mackenzie]

Hello, Gentoo.

I've just bought myself a Samsung NVMe 960 EVO M.2 SSD.  (Do I get a
prize for the number of inscruitable abbreviations in a row? ;-)  The
idea is, this will form a core part of my new machine, just as soon as
AMD Ryzen motherboards start being reasonably available.

I put it into my current (7½ YO) box to test it out.

Physically installing it was no problem at all - I also bought a PCIe
carrier card with an M.2 slot.  Making Linux see it was also no sweat -
I just added the appropriate settings to the device driver bit of the
kernel's menuconfig (as detailed in the Gentoo NVMe wiki page), rebuilt
and re-installed it and it worked.

I'd had some slight worry about how to actually drive this thing.  The
night before, I'd emerged sys-apps/nvme-cli, and became bewildered by
all the things it appears you need to understands for NVMe drives.  But
my new SSD, /dev/nvme0, already carried a "namespace", /dev/nvme0n1.
Before long, the "namespace" had an MS-DOS partition table and two 20GB
ext-3 partitions, just to try it out.

I copied /usr/portage onto one of these partitions and mounted it at
/usr/portage.  I mounted the other one at /var/tmp.

Some timings:

An emerge -puND @world (when there's nothing to merge) took 38.5s.  With
my mirrored HDDs, this took 45.6s.  (Though usually it takes nearer a
minute.)

An emerge of Firefox took 34m23s, compared with 37m34s with the HDDs.
The lack of the sound of the HDD heads moving was either disconcerting
or a bit of a relief, I'm not sure which.

Copying my email spool file (~110,000 entries, ~1.4 GB) from SSD -> SSD
took 6.1s.  From HDD RAID -> HDD RAID it took 30.0s.

#########################################################################

I must confess to feeling somewhat underwhelmed by this new SSD.  I'm
quite some way off of the advertised ~3 GB/s read speed and ~1.5 GB/s
write speed (which admittedly needs PCIe version 3).  Quite likely, I've
not got the drive set up optimally, but I think it's connected to the
rest of the PC via four PCIe version 2 lanes.  (I'll need to work out
how to check this.)

But in a pure file copy, I'm only getting a factor 5 speed increase over
my 7½ year old HDD pair.  Doing portage things, it's shaving only modest
factors off of the timings.

My intention was to have a RAID pair of these NVMe drives in my new box.
Now I'm thinking more along the lines of using this NVMe drive for the
OS, and a RAID pair of (cheaper) SATA SDDs for precious data - the extra
performance that NVMe gives over SATA, although more significant with a
modern speed machine than my 7½ year old one, seems unlikely to justify
the extra cost.

-- 
Alan Mackenzie (Nuremberg, Germany).