[conspire] external storage recommendation

[Rick Moen]

Quoting Paul Zander (paulz at ieee.org):

> Yes, simple external USB drives are the EASY button. 
> 
> Several TB flashdrives will cost much less. They don’t take up desk
> space, don’t consume power when not in use, and don’t have proprietary
> software. What’s not to like?

Possibly file-transfer time?  Not sure,  Worth checking.

Upthread, I found credible real-world estimates of MB/sec transfer rates
typical in copying to external HDs via USB2 transport.  I'm not certain
offhand how the same bulk copy to a USB2-capable flash drive would
compare.  I fear it might be substantially slower.  Remember, I
guesstimated a worst-case initial copy of an almost-full 1/2TB memory
stick to a USB2 external drive as 5 hours.

It's a little hard to find that real-world data.  E.g.,
https://recoverit.wondershare.com/usb-tips/fix-usb-transfer-speed-slow.html
says "For reference, the transfer rate of USB 2.0 is 480Mbps (Megabits
per second", which is nice to know, but that knowledge plus $3.00 will
get you a ride on Muni.  Which is to say, it's a _ceiling_ on the
fastest possible transfer over a USB2 bus, but tells you nothing
whatsoever about actual speed with real devices.

http://usbspeed.nirsoft.net/?g=largedisk has a collection of what are
said to be real-world speed test results.  Notice that, predictably, the
read speeds are a good bit higher than the write speeds, and values of
write speeds vary quite a bit, from around 3MB/sec to a bit over
50MB/sec (one extreme outlier), with most landing in the 17-22 MB range.
So, call 20MB a common figure -- but with a lot of variation.

Upthread, I said "Typical hi-speed USB 2.0 hard drives can be written to
at rates around 25-30 MB/s, and read at 30-40 MB/s."

So, there's your answer.  You lose _some_ transfer speed.

Flash drives fail.  Hard drives fail.  But the way they do differs a
bit.  Often but not always, the HD gives you some advance warning &
clues (e.g., noises) before biting it.


By the way, to quibble:  External HDs _also_ don't consume power when
not in use, and don't have proprietary software (unless you're counting
the firmware, but that's a broader issue).  Nor do they need to take up
disk space.  You detach them and put them in a drawer, same as a USB
flash drive -- but of course are larger.

(I'm betting you were implicitly comparing flash drives to off-the-shelf
_NAS_, rather than comparing flash drives to external, USB2-connected
HDs -- in saying one takes no power when not in use, doesn't take up
room on a desk, and doesn't have proprietary software.)

Sorry to keep hounding you on this but because you said you want
_backup_, not that you want a network-live, online copy (e.g., NAS), it
is a significant and vital aspect of backups that you can remove them in
some fashion from the risks the original data location undergoes, so
that the same loss threat doesn't take out both copies.  The most
straight-forward, old-school method of preventing common-mode lossage is
to physically detach and remove the backup copy, preferably storing it
offline for safekeeping, and preferably offsite -- or at least, at a
considerable distance.

Why?  Let me make that vivid, through some examples.

A lot of system administration involves stopping and thinking "What am I
going to do if $THING fails?" for diverse values of $THING.  

o  A residence fire (or a fireman's water hose, or smoke) destroys 
   both your system and all its backups.  Oops.
o  A burglar steals both your system and all backups.  Oops.
o  Your house's incoming AC neutral lead breaks at the roof
   line[1], subjecting all electronics in the house to 2x normal
   voltage.  All your computers got fried simultaneously,
   including the NAS that was your sole backup.  Oops.
o  Your house suffers Internet security breach because you 
   relied on a lousy SOHO gateway box for security protection,
   and every online device in your house got security compromised
   and encrypted by ransomware criminals, including the NAS
   that was your sole backup.  Oops.

The last two examples illustrate two of the reasons I said "NAS is not
backup", and there are many others.

Really.  A live onlne copy isn't really backup, for a whole range of
reasons involving diverse ways badness can happen.


[1] This happened at our house.  Some electronics was damaged, but 
we unplugged everything before major lossage could occur.