"the mind is the 2nd thing to go and I don't remember the first". Is the quote of a previous quote a 2nd level quote? Anyway, I remember what I was trying to do with the OSA. I didn't really attach the OSA card to Linux. However, my original question did bring out a good discussion. In a previous IFL/Linux/POC, we set up a Linux running UDB. We wanted to allow access to that Linux from two sources: existing mainframe apps. and apps. running on WAS (IBM web app. server). I set up a virtual lan (hiper-sockets and such) for the apps on the mainframe to get to UDB. For the WAS part, I used 3 addresses from an OSA card, DEDICATED those to the Linux/UDB guest. This allowed WAS to avoid going through the VM TCPIP stack and through the virtual lan to get to UDB, in essence reducing the length of the path taken to get to UDB. It all worked. Good idea? Not so good an idea? Steve G.
-----Original Message----- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Alan Altmark Sent: Thursday, April 24, 2008 11:24 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: OSA rdev and vdev requirements for Linux guests. On Thursday, 04/24/2008 at 10:27 EDT, "Gentry, Stephen" <[EMAIL PROTECTED]> wrote: > Ok, I'll ask. Why wouldn't one attach an OSA card directly to a Linux > guest? > Seriously, why shouldn't this be done? Off the top of my head: (a) Security. You now limit what can be done with the OSA since you give it to a guest to use. You wouldn't want to share it with other guests (IMO). Do you know what low-level functions are available in the OSA? Me neither, but a virtual NIC is designed to prevent a guest from doing things you don't want it to do or limiting the scope of what it does. And I certainly wouldn't even THINK about letting a guest have arbitrary access to all your VLANs unless it is supposed to have that access. (b) High availability. If a guest is handling the OSA, then the guest must handle any OSA, cable, or switch errors or device outages. The VSWITCH handles that transparently for all guests using the VSWITCH. What if you have 5 guests that need OSAs? Each would need a backup as well. (c) Utilization. Who is using the OSA when this guest isn't? Does it sit idle? A VSWITCH operates an OSA on behalf of multiple guests. Alan Altmark z/VM Development IBM Endicott
