Re: Filesystem errors on armv7 -current

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. I'll let it continue and look for another
suitable wallwart in the meantime.

Thanks for writing!

bob prohaska