Re: [Xen-devel] xenolinux /dev/random

[Steve Traugott <stevegt@xxxxxxxxxxxxx>]

The server is debian woody, 2.4.21.  

I've never seen any obvious way to actually set any timeout, block
size, or other parameters for an NFS root partition -- and it seems to
ignore whatever's in fstab, which makes sense.  

Right now the only reason I'm even using NFS is because a Xenoserver
provider needs to be able to do backups, migration, failover, and so on.
How are other people meeting these requirements?  Has the CoW
development stalled?  What about live migration?

Steve

On Thu, May 13, 2004 at 07:54:57AM -0700, Kip Macy wrote:
> Are you also using Linux as an NFS server? We use Linux extensively
> in-house for client machines and have not seen this. Although I'm sure
> we don't use the default Linux settings.
> 
> 
>                               -Kip
> 
> 
> On Thu, 13 May 2004, Steven Hand wrote:
> 
> >
> > >My goodness!  See the message I just now posted to xen-devel about NFS
> > >root hangs; could this be what we're hitting?  The most recent hang we
> > >saw happened while an rsync was running over ssh *and* someone restarted
> > >apache...
> > >
> > >This wouldn't cause the "NFS server not responding/NFS server OK"
> > >messages on the domain's console, though (or does that show up as a
> > >symptom of this too?)
> >
> > I don't think this is the cause of the NFS hangs you've been seeing; that
> > appears to be a generic linux thing (at least we see it with our regular
> > linux boxes as well as with xen boxes); however if you want to test the
> > theory the easiest thing to do is to change the /dev/random device node
> > to be an alias for /dev/urandom (a non-blocking but potentiallyweaker
> > source of randomness).
> >
> > The /dev/random bug only really manifested for us during boot, only on
> > Xen, and resulted in a permanenent hang.
> >
> > The "NFS server foo not responding" followed by later "NFS server foo OK"
> > messages from linux appear to be due to a combination of stupid timeouts
> > in the linux sunrpc code and another bug which can cause automounters
> > to fall into an uninterruptible sleep. If you check "ps auwwx" on a
> > machine which is having problems and notice proceesses in state 'D'
> > then this is biting you. Even if this doesn't occur, the crappy timeouts
> > in the regular linux code mean that linux perfroms very badly if it gets
> > any errors/loss/congestion during nfs operations.
> >
> > cheers,
> >
> > S.
> >
> >
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-- 
Stephen G. Traugott  (KG6HDQ)
UNIX/Linux Infrastructure Architect, TerraLuna LLC
stevegt@xxxxxxxxxxxxx 
http://www.stevegt.com -- http://Infrastructures.Org