James:
thanks for the corrections, I'm not an NFS guru.
However, I would caution you to never say never ;-) I
have dealt with this problem in the past concerning NFS
and the mounted filesystem falling off the face of the
earth, NBU kept on writing (creating new directories,
etc.). I watched it happen, it can and has happened.
Thanks again for your help in correcting me.
David
Quoting James Mello <kingjamm AT colltech DOT com>:
> > I may be wrong here, but NFS was designed
originally as
> > a connectionless protocol,
>
> Actually it was written as a *stateless* protocol.
Every transaction was
> (and still is to a certain degree) atomic and
shouldn't rely on the
> previous transaction. It is perfectly acceptable to
have a stateless
> protocol be connection oriented. HTTP is a perfect
example of this.
>
> > In a NBU environment if that should happen, it
> > potentially hang and hang until failure occurs and a
> > blocking of your backup window. Ultimately you will
> > pay the price of incomplete backups.
>
> >From *nix's perspective loosing an NFS drive is akin
to loosing a disk. If
> a disk were to fail fails, NBU can't do it's work
either. But, in a proper
> NFS environ, this would be HA and it going down
wouldn't be an issue.
>
> So unless the network transport fails, or a disk
dies, there shouldn't be
> an issue with timeouts. This is the *exact* same
kinds of issues that SANs
> based storage has to deal with. If the transport
dies, then you're SOL.
>
> > Alternatively, one may use hard mounts (as I know
them
> > to be called) which will NOT wait when a NFS
filesyetem
> > should become unavailable, but will terminate the
> > connection.
>
> Hard mount behavior is to do the waiting. Soft mounts
on the other hand
> will return an error and possibly corrupt data. From
the Solaris man page
> for mount_nfs
>
> soft|hard Return an error if the server does
not
> respond, or continue the
retry request
> until the server responds.
The default
> value is hard.
>
> > written to the mount point and not the NFS filer you
> > want it to.
>
> That will *NEVER* happen as the filesystem has been
mounted over. In unix,
> once something is mounted, it doesn't disappear
unless it's told to
> explicitly via a umount.
>
> -- Cheers
> -- James
>
>
>
<><><><><><><><><><><><><><><><><><><><>
David A. Chapa
Consulting Manager
DataStaff, Inc.
847 413 1144
http://www.consulting.datastaff.com
---------------------------------------
http://www.xbpadm-commands.com
NBU-LSERV AT datastaff DOT com - Adv. Scripting
|
