Re: xbd IO domain 2: error 5 (Xen2, NetBSD 3.0)

[Johan Ihren <johani%johani.org@localhost>]

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On 5 Oct 2006, at 23:19, Manuel Bouyer wrote:

> On Thu, Oct 05, 2006 at 11:09:42PM +0200, Johan Ihren wrote:
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> > Hi Manuel,
> >
> > > > for one thing: I now see a sprinkling of
> > > >
> > > >         "xbd IO domain 2: error 5"
> > > >
> > > > in the logs and on the console. Never saw that before. It is always
> > > > "domain 2" (which is started at boot) and always "error 5" (which I
> > > > assume is "IO error" a la errno.h). I haven't noticed any real
> > > > problems, though, everything *seems* to still work fine.
> > > >
> > > > But I sure would like to know what the problem is (especially if  
> > > > this
> > > > signals a REAL problem somewhere) and why it arrived in combination
> > > > with the disk replacement. Any ideas?
> > >
> > > Is it a physical partition or a vnd ?
> >
> > vnd
> >
> > > If it's a physical partition make sure you didn't make it too short.
> > > If it's a vnd, make sure you can read the whole file, and that it
> > > didn't
> > > get truncated.
> >
> > There were no errors during dump/restore from old disk to new disk.
> > The file has the correct size and I'm able to read it all from the
> > Dom0 without any errors.
>
> Hum, can you dd from /dev/rvnd0d to /dev/null the whole device ?
> If the error comes from xbdback itself, there should be another error
> message before this one.

Stupid me, I checked that I could read the *file* not the *device*:

dom0-1:store/xen#dd if=vm/master.img bs=8192 of=/dev/null
49152+0 records in
49152+0 records out
402653184 bytes transferred in 9.437 secs (42667498 bytes/sec)

The device does indeed show an error:

dom0-1:store/xen#vnconfig -c vnd0 vm/master.img
dom0-1:store/xen#dd if=/dev/rvnd0d bs=8192 of=/dev/null
dd: /dev/rvnd0d: Input/output error
6014+0 records in
6014+0 records out
49266688 bytes transferred in 1.501 secs (32822576 bytes/sec)

Hum. You were spont on, the filesystem is indeed truncated. So I  
tried to recover by mounting the image and constructing a new, clean  
one with makefs and now the evidence is plain to see:

dom0-1:store/xen#makefs -t ffs -b 256m -f 10000 vm/master.2.img tmpmnt
Calculated size of `vm/master.2.img': 429924352 bytes, 16581 inodes
Extent size set to 8192
vm/master.2.img: 410.0MB (839696 sectors) block size 8192, fragment  
size 1024
        using 8 cylinder groups of 53.45MB, 6842 blks, 2240 inodes.
super-block backups (for fsck -b #) at:
     32, 109504, 218976, 328448, 437920, 547392, 656864, 766336,
Populating `vm/master.2.img'
makefs: Reading `tmpmnt/usr/mdec/netboot_ne2000_isa.rom', 8192 bytes  
to go: Input/output error

Many thanks for the quick help, Manuel. Now that I know what has  
happened I'll recreate the image from another source.

Regards,

Johan


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