Re: [gpsd-users] Fwd: Re: 1PPS not working with RPi 3 B+ and Stretch

[Gary E. Miller]

Yo Alan!

On Thu, 26 Jul 2018 12:02:23 -0700
Alan Scott <address@hidden> wrote:

> this dd - zeros should eliminate that issue.......

Not a good idea with SD cards.  Each block on the SD card can only be
written to a limited number of times before it is unuseable.

Some SD cards die after just 500 full card writes.

Worse, SD cards have spare blocks and use wear leveling.  So when
you dd zeros you are not over writing the old data, just writing
to spare sectors.

Some cards support "fstrim".  That tells the SD card to mark unused
blocks as empty, without wasting a write cycle.

I find, confirmed by others, that some cards prefer some adapters over
others.  Some suggest never using a USB3 adapter with SD cards.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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