Re: Problem with 2.6 kernel and lots of I/O

[Kyle Moffett]

On Jun 5, 2005, at 06:11:02, Erik Slagter wrote:
> On Wed, 2005-06-01 at 21:59 +0200, Pavel Machek wrote:
>
> > >     Start RAID in degraded mode with remote device (nbd1)
> > >     Hot-add local device (nbd0)
> >
> > Stop right here. You may not use nbd over loopback.
>
> Any specific reason (just curious)?

IIRC, because of the way the loopback delivers packets from the
same context as they are sent, it is possible (and quite easy)
to either deadlock or peg the CPU and make everything hang and
be unuseable.  DRBD likewise used to have problems with testing
over the loopback until they added a special configuration
option to be extra careful and yield CPU.

Cheers,
Kyle Moffet

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