RPI3 swap experiments

[Mark Millard]

On 2018-Jun-27, at 7:24 PM, bob prohaska <fbsd at www.zefox.net> wrote:

> On Wed, Jun 27, 2018 at 06:12:53PM -0700, Mark Millard wrote:
>> On 2018-Jun-27, at 12:42 PM, bob prohaska <fbsd at www.zefox.net> wrote:
>> 
>>> On Tue, Jun 26, 2018 at 11:30:52PM -0700, Mark Millard wrote:
>>>> . . .
>> 
>>>> For (B), have you tried any examples of:
>>>> 
>>>> insufficient swap on (say) mmcsd0 and no use of the
>>>> /dev/da0 drive that has reported errors at all,
>>>> /usr/ and /var not on mmcsd0 (or whatever was used
>>>> for swap) either? Did some drive end up reporting
>>>> errors? Which? Did the system still crash as well?
>>>> 
>>> I think this is the standard test case:
>>> /usr and /var on /dev/da0
>>> /tmp on /dev/mmcsd0s3a
>>> swap on /dev/mmcsd0s3b
>>> 
>>> This configuration has crashed reliably with errors on /dev/da0 but no other "disk" errors.
>>> Did I understand the question correctly?
>> 
>> I intended for "no use of /dev/da0" to indicate
>> that not even /usr or /var were from the device
>> that has been logging the errors. For example:
>> having /usr or /var on the mechanical disk and
>> the known-problem disk not connected at all.
>> 
> Not yet, but absent new developments I'm running out of
> other things to try. My hesitations stems partly from my
> own sloth, but mostly from a concern that I'll introduce
> confounding changes unintentionally. I'm hopeful Jaimie
> will get his Pi3 running and see something interesting.
> 
> Some time ago I asked whether it would be better to
> dd the existing da0 onto another device or better to
> construct a complete new installation (new snapshot
> on a new microSD plus a new USB thumb drive). Would
> you venture a guess?

/dev/da0 is logging write errors. fsck does not
correct individual blocks that are part of the content
of a file. /dev/da0 is also logging read errors, and,
again, fsck does not correct individual blocks that are
part of the content of a file. (fsck works on the file
system that describes information for finding/using
files and their content. [simplistic description])

So I would not trust a copy of /dev/da0 to have avoided
the copying already-existing (as read) corruptions of
the intended content in various places.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)