On Monday, 03/26/2007 at 09:53 EST, Brian Nielsen <[EMAIL PROTECTED]>
wrote:
> On Fri, 23 Mar 2007 09:55:05 -0400, Alan Altmark
<[EMAIL PROTECTED]>
> wrote:
>
> >It is also my
> >recommendation that you do not share an OSA in use by a VSWITCH,
> >*especially* if it is VLAN-aware. The last thing you want is a fight
> >between two VSWITCHes about whether a VLAN is in use. Yes it is, no it
> >isn't, yes it is, no it isn't.... If you choose to go down this path,
> >define the VSWITCH with NOGVRP.
>
> Would you please eloborate on this? I have multiple VLAN-aware
VSWITCHes
> sharing the same OSA with no problems. Each VSWITCH has a distinct and
> separate set of VLANs, if that makes any difference. This setup is
> required to connect non-VLAN-aware guests to multiple VLANs via VSWITCH
> GRANTs.
>
> If there is a pitfall in there somewhere I'd like to know more about it.
As long as you do not try to span VLANs across different VSWITCHes sharing
an OSA, it will work. The problem I run into is that someone changes the
switch (virtual or real) or VLAN configuration without thinking about the
affect on a shared port. Things start to fail. But it's just a
recommendation, not a requirement. Our gun. Your foot.
In z/VM 5.3 we announced support for IBM System z9 IEEE 802.1ad Link
Aggregation ("channel bonding", "etherchannel"), providing additional
bandwidth with each OSA you add to the "aggregation group". In this
configuration, the OSAs are usable by only a single VSWITCH at a time, and
will use additional hardware support to enforce this. (There is a
switch-to-switch protocol flowing over the links along with user data and
more than one cook in the kitchen will spoil the broth...) Imagine up to
80 Gb of data per second moving in/out of the box (up to eight 10 Gb
ports).
This support also provides for the smooth addition or removal of OSAs from
the aggregation group, whether because you want to add/take an OSA, or
because one fails. No data is lost, with retransmission handled at a
packet level rather than at the TCP segment level.
If you ever think you will want to take advantage of this support, you
need to be planning for dedicated OSAs, even if you need to share right
now.
And, of course, mixing VLAN-aware and non-VLAN-aware is a no-no, though
nothing will enforce it.
So, none of this is really about what *can* be done. You can share all
you want. But the risk to your virtual data center is lowest if you don't
share, and that remains my recommendation.
Admittedly, "because Alan says so" only goes so far (the "Wesayso
Corporation", anyone?). I have the same problem at home. Go figure. :-)
Alan Altmark
z/VM Development
IBM Endicott
