[PLUG-TALK] SSHD accelerated drives Re: SSD lstat ...

[Keith Lofstrom]

On a slightly different subject, rotating magnetic disk
hard drives with substantial solid state "caches" are
far less expensive than pure solid state drives.  I'm
about to deploy a Seagate ST1000LM014 laptop drive, with
1000 GB of disk and 8 GB of NAND flash.  Supposedly,
the drive uses the NAND flash as a cache for frequently
read sectors.

I have no idea how well it will perform with Linux;
perhaps it is incompatible, or optimized for Windows,
or optimized for new versions of Windows designed to
work with such drives.

I will deploy it with a clone of Red Hat Enterprise
Linux version 7 (3.10 kernel) on an older laptop. 
Specifically, I will first get the distro working on
an older 500 GB traditional drive, then copy that
working image to a 1000 GB Seagate for the same laptop.

SO, THE QUESTION FOR THE LIST, which may have some
relevance to the SSD lstat question; how do I perform
an objective before-and-after test of the usability
and speed, beyond boot time?  What simple tests would
you folks like me to do?

My personal interest is reliability, not speed.  Hard
disks fail because moving parts wear out; the fewer head
accesses I make to the platter, the better.  OTOH, solid
state drives tend to fail because the write process
involves higher voltages, which wears out the electronics.
Solid state read access can be very fast, yet involve
less stress than swinging heads across a rotating platter
for read or write, and both of those less than a solid
state write operation.

If the drive is versatile enough to optimize the SS as
a cache for frequently accessed sectors for LINUX, this
is a win-win.  On the other hand, if the drive does not
accomodate the way Linux uses a disk, it could be a big
disappointment.  On the third hand, a Linux file system
optimized for these drives might be superhigh performance.
On the fourth hand, these drives are new and their
behavior will evolve, so a file system optimized for a
2016 SSHD drive might be terrible for a 2018 SSHD drive.

I have a 50% deficit of hands here, so I could use a
hand or five from the rest of you.  What should I test? 
Send code (compilable or RPM), not vague suggestions for
tests I have no clue how to code or perform.  Thanks!

Keith

-- 
Keith Lofstrom          keithl at keithl.com