[talk] SD cards for Pi?

Brian Reynolds nycbug-talk at reynolds.users.panix.com
Sun Nov 19 18:13:41 EST 2017

[I did not realize that nycbug-talk does not reply to the list (at
least with mutt), so I'm (again) resending this (lightly edited).]

I have several Raspberry Pis running 24 hours a day at various loads.
Most of them run one of several different Linux distros intended for
specific tasks.

In particular I have a Raspberry Pi 2 model B running LibreELEC
hanging off my TV.  I use it to watch various videos I download from
the Internet to the SD card used to boot the RPi.  I frequently fill
and empty this card.  Downloading new videos while simultaneously
viewing other videos can tax both the IO system and CPU on the RPi.

I find that the most important factor for SD card stability with the
RPi is power supply quality.  If your power supply is flaky, or on the
low end of the recommended power range you can expect trouble.  Since
switching to 2.5A power supplies from good vendors (Adafruit, Micro
Center) I haven't had trouble.

Charles Sprickman wrote:
> So two questions:
> - At a local Walgreens or Staples, what???s a decent SD card?  I
> know nothing of these things.

I tend to use SanDisk SDHC or microSD cards, mostly because that's
what I use for my photography.  Cards with Class 10 or U3 ratings
should be fast enough.

At last month's Photo Plus Expo I asked the representative at the
SanDisk booth about which card to use for SBC filesystems.  He hadn't
realized that anyone was using SD cards that way, but suggested that I
look for cards used for surveillance cameras on their website.
Unfortunately their website is big on flashy presentation, and low on
technical content.

> - Is there any tweaking I should have done to FreeBSD to make it not
> write excessively to the card (I did not have swap enabled)?

.ike has good ideas on changes you could make.

I have a lightly loaded original Raspberry Pi Model B (256MB RAM)
running FreeBSD 10.2-STABLE that I use for fiddling around.  Without
my making changes, it has /tmp as mfs in /etc/fstab.  I assume .ike's
recommendations are for more recent releases.

I'll eventually update the release on this RPi, and I may get back to
my experiments in booting FreeBSD off of a hard disk instead of the SD
card.  On older models you need an SD card to hold the FAT filesystem,
but root (and other partitions) can be on a USB drive.  I got this far
a while ago.  On the Raspberry Pi 3 model B there is beta support for
hard disk, or network booting without a SD card.  I have not tried
this with FreeBSD yet.

Brian Reynolds                   | "It's just like flying a spaceship.
reynolds at panix.com               |  You push some buttons and see
https://www.panix.com/~reynolds/ |  what happens." -- Zapp Brannigan
NAR# 54438                       |  

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