gmirror + usb problem

srwadleigh srw at
Sat Oct 28 18:33:37 UTC 2006

On Sat, 28 Oct 2006 13:22:06 +0200
Brian Josefsen <bj at> wrote:

> srwadleigh wrote:
> > On Fri, 27 Oct 2006 01:26:11 -0400
> > srwadleigh <srw at> wrote:
> >
> >   
> >> Thinkpad T41
> >> 6.2-PRERELEASE FreeBSD 6.2-PRERELEASE #20: Thu Oct 26 05:15:07 EDT
> >>
> >> Two usb attached WD myBook 500gb external drives. The first drive
> >> is setup as a gmirror provider, and mounts/functions fine, when I
> >> attempt to add the second external drive it detects but will not
> >> rebuild, it simply remains at 0%, no drive activity.
> >>
> >> Following the attempt to rebuild any attempt to stop the providers
> >> or remove the stale drive causes the system to lockup or rather
> >> become almost entirely unresponsive. Responds to pings, moused
> >> input works, existing ssh sessions still function, but cannot
> >> login, execute new commands, or get output without serious delays,
> >> sometimes--eventually the system snaps back and everything is fine
> >> but it can take a very long time. Nothing seems to entice the
> >> second provider to sync up.
> >>
> >> I have tried setting gmirror to auto rebuild and manual, both yield
> >> the same result. I have also tries each drive as the first
> >> provider, again with the same results either way. Also tried
> >> gmirror compiled in and as a mo
> >>
> >> I'm not sure if this is gmirror, usb, or the combo of the two
> >> elements, or maybe even something with the mybook.
> >>
> >>     
> >
> > An addition, the second provider does rebuild, just extremely
> > slowly, according to the activity lights moving data only in short
> > bursts spaced by long periods of inactivity. In the last eight
> > hours the provider has reached 2%.
> >   
> Hi
> I'm no expert here but, i would suspect that the proces is slow
> because the usb controller is fighting for the bandwidth same way as
> if you try to shift data from ad0 to ad1, perhaps use another usb
> port for one of the disk and check top to see if usbd is having a
> hard time. In general though i know that usb isn't the most fantastic
> place to store your data as the intermediate controller can't push
> the information about bad blocks etc. through usb.
> --
> Med venlig hilsen / Best regards
> Brian Josefsen
> Copenhagen, Denmark

That sounds quite possible, the one curious thing is rsyncing between
the two drives, while it takes a long time to copy the full capacity,
the drives do work continuously. Same two usb ports in question.

It seems to me if rsync can run a big copy gmirror would be doing
something similar but at a lower level, and maybe that makes all the
difference to the usb controller. 

Soon I will have another system available to test with, likely better
usb controller and firewire. 


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