Re: [RFC][PATCH 0/9] Network receive deadlock prevention for NBD

Peter Zijlstra
2006-08-14T06:45:43Z

On Mon, 2006-08-14 at 09:13 +0400, Evgeniy Polyakov wrote:
> On Sun, Aug 13, 2006 at 01:16:15PM -0700, Daniel Phillips (phillips@google.com) wrote:
> > Indeed. The rest of the corner cases like netfilter, layered protocol and
> > so on need to be handled, however they do not need to be handled right now
> > in order to make remote storage on a lan work properly. The sane thing for
> > the immediate future is to flag each socket as safe for remote block IO or
> > not, then gradually widen the scope of what is safe. We need to set up an
> > opt in strategy for network block IO that views such network subsystems as
> > ipfilter as not safe by default, until somebody puts in the work to make
> > them safe.
>
> Just for clarification - it will be completely impossible to login using
> openssh or some other priveledge separation protocol to the machine due
> to the nature of unix sockets. So you will be unable to manage your
> storage system just because it is in OOM - it is not what is expected
> from reliable system.
>
> > But really, if you expect to run reliable block IO to Zanzibar over an ssh
> > tunnel through a firewall, then you might also consider taking up bungie
> > jumping with the cord tied to your neck.
>
> Just pure openssh for control connection (admin should be able to
> login).

These periods of degenerated functionality should be short and
infrequent albeit critical for machine recovery. Would you rather have a
slower ssh login (the machine will recover) or drive/fly to Zanzibar to
physically reboot the machine?