lkml.org 
[lkml]   [2006]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC][PATCH 0/9] Network receive deadlock prevention for NBD
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.

The system is not OOM, it is in reclaim, a transient condition that will be
resolved in normal course by IO progress. However you raise an excellent
point: if there is any remote management that we absolutely require to be
available while remote IO is interrupted - manual failover for example -
then we must supply a means of carrying out such remote administration, that
is guaranteed not to deadlock on a normal mode memory request. This ends up
as a new network stack feature I think, and probably a theoretical one for
the time being since we don't actually know of any such mandatory login
that must be carried out while remote disk IO is suspended.

>>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).

And the admin will be able to, but in the cluster stack itself we don't
bless such stupidity as emailing an admin to ask for a login in order to
break a tie over which node should take charge of DLM recovery.

Regards,

Da niel
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-08-17 06:53    [from the cache]
©2003-2011 Jasper Spaans