[OpenIndiana-discuss] Recovering from power loss on USB ZFS pool?

[Michael Stapleton]

I'm not sure when things changed, but way back in the OpenSolaris days,
I had the root drive in my laptop mirrored to an external USB drive.
I never had problems back then. I would do a demonstration where I would
remove the USB drive while the laptop was up and running, and then plug
the USB submirror into another laptop and boot from it.
Never had a problem. I could even reattach the USB drive to my laptop
and it would resilver automatically. 

Is the problem ZFS or USB or FMA? no idea. But the was a regression of
sorts.
I don't think Solaris11 suffers from this.


Mike



 On Thu, 2014-03-27 at 18:39 +0000, Jonathan Adams wrote:

> On 27 March 2014 18:28, Reginald Beardsley <pulaskite at yahoo.com> wrote:
> 
> > What's the correct way to recover from loss of power to a USB disk based
> > pool?
> >
> > I cleverly unplugged the wrong wall wart from the power strip behind my
> > monitor and dropped power to a USB disk that was being written to.  The
> > system stayed up, but any attempt to restart or kill the write operation
> > failed and attempts  to query the status of the pool hung.  I tried to
> > restart the system, but that hung also and ultimately I forced the system
> > down w/ the power switch.  It rebooted w/o any problems.
> >
> > The  SATA drive scrubs showed they were  OK.  The USB scrub is still
> > running, but the pool seemed OK after the reboot.
> >
> > Surely there is a better way to recover from such things than just killing
> > the power.  google didn't seem to have any suggestions so I thought I'd ask
> > here.
> >
> 
> from my experience with USB zfs systems, there is no better way :(
> 
> >From my experience, when a USB drive goes off on one (doesn't necessarily
> even need powering off) it kills the whole ZFS until the point that you
> have to reboot the machine, as long as you don't have too many USB devices
> plugged in on a reboot it should recover and scrub happily.
> 
> We have had several machines with USB drives that caused us problems.
> 
> 1) we have a machine with an irregularly used USB drive ... sometimes the
> drive fails to talk to ZFS when it is waking up out of sleep mode ... the
> only reason we can reboot that one is that it's a Solaris 10 with UFS root
> filesystem
> 2) we had big Arrays > 8 disks plugged in over USB ... if we had plugged a
> keyboard in during it's uptime, and forgot to unplug it the drives wouldn't
> import, if we plug the keyboard in the front sockets of the machine the ZFS
> hangs.
> 
> strangely enough we don't have any more free floating ZFS usb drives (6
> T710's bought to house the USB arrays internally) except to perform
> sneakernet operations.
> 
> on a positive note, taking an unreliable old USB ZFS pool off of a
> misbehaving Solaris 10 box and plugging into an Ubuntu with ZFS allowed the
> USB drive to work flawlessly for a long time thereafter ... Ubuntu ZFS
> seems a lot more stable and reliable than the Solaris/Illumos equivalent.
> If you have future trouble (and you haven't upgraded your ZFS on Illumos to
> the latest greatest hipster version) you should be able to get your data
> back.
> 
> Jon
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