Re: Filesystem errors on armv7 -current

On Thu, Oct 22, 2026 at 06:40:02PM -0700, Mark Millard wrote:
> On 10/22/26 18:03, bob prohaska wrote:
> > On Thu, Oct 22, 2026 at 02:45:53PM -0700, Bakul Shah wrote:
> >> On Oct 22, 2026, at 6:35 AM, bob prohaska <fbsd@www.zefox.net> wrote:
> >>>
> >>> On Wed, Oct 21, 2026 at 10:32:07PM -0700, Bakul Shah wrote:
> >>>>
> >>>> One can buy a cheap inline USB power meter or tester to see
> >>>> what sort of voltage/current is in use. Fancier ones such as
> >>>> FNIRSI FNB48P that will let you see a realtime graph of
> >>>> voltage/current at various sampling rates + you can upload
> >>>> this data (+ there is vibe coded s/w to run on linux/mac for
> >>>> this as well). Very useful for debugging this sort of
> >>>> problems.
> >>>
> >>> I have chopped a USB cable to bring out the power leads and
> >>> connected them to a voltmeter in the past. That would seem
> >>> adequate to identify a faulty power supply. I haven't tried
> >>> it in this specific case, but  given the absence of messages
> >>> from umass other than those at boot, is there any point?
> >>
> >> The boot umass messages were fine.
> >>
> >> The problem is you are dealing with potentially marginal
> >> devices that may misbehave under load and no guarantee that
> >> software or firmware will catch such errors. By default the
> >> pi2b  limits total current (across all 4 USB ports) to 600
> >> mA.  You can add 'max_usb_current=1' to config.txt to
> >> increase it to 1.2A (IIRC) - provided Pi's power supply is
> >> capable.  [Some earlier HDD USB disks came up with weird USB
> >> cables for plugging into *two* ports to get enough power!]
> >>
> >> It may be that the problem you're seeing is software related
> >> but such USB measurements can clearly eliminate power as an
> >> issue.
> > 
> > The disk is not powered by the Pi2, but rather by its own 
> > powered hub.  A USB cable plugged into the hub shows 5.15 
> > volts on a DVM, an oscilloscope reveals fluctuations down 
> > to about 4.86 volts over tens of milliseconds. ISTR the Pi
> > should work down to about 4.75 volts, haven't found a number
> > for the disk.
> > 
> > Just for fun, I wiggled the DC jack on the powered hub and
> > the DC voltage came up to 5.23 volts with about 70 mV P-P
> > of roughly 2 kHz hash on the line. Maybe that's the switching
> > frequency, I've never made this measurement before.
> > 
> > The machine is still running buildworld, so far without obvious
> > errors or faults.
> 
> Failing parts of the disk that are supposed to have directory related
> content but that are not being accessed are not going to report those
> known errors.
> 
> A more effective test would be something that would read every (most
> every?) block of the disk and report any failed-to-read blocks. (I limit
> to read only testing to avoid destroying data. Other than if you have
> atime updating enabled, find likely would be complaining about read
> activity to exclusion as well --but on a subset of the blocks.)

For the moment I'm more concerned about the amount of noise/hash
on the power supply lines. A similar measurement on a second Pi2B
setup seems to show about an order of magnitude less rubbish. I
don't know how much is too much, but the troublesome Pi/hub/disk
is quite noticeably worse than the second one tested. The comparison
hasn't been done with enough care yet to have much confidence
either way, I hope to remedy that situation in the next few days.

If you're suggesting the disk itself might be the culprit, that's
something I hadn't considered until just now....hmmmm.

Thanks for writing,

bob prohaska