So, are you saying that the new NetApp failover system has two toasters hooked up to the same RAID set, and then the secondary toaster will mirror the state of the primary toaster? Can they share the same NFS state, including file handles and such, so that there are no dead/stale handles? Ok, I have a more abstract question about HA (high availability) in general. Here's what I know. There are many delicate issues involved in HA, that stem from the fact that you're using technology that's primarily designed as standalone. In other words, it's a group of _individual_ hosts. The issues happen because you're trying to get one host to dynamically assume the identity of another host, on some level or all levels. Am I wrong on any of that? So my question is, what are the main factors involved? I know what happens when you have a high-level router, switch, bridge, etc and you swap an ethernet card in a machine. It won't work until you call your router admins and have them reset the arp cache :) I'm guessing that this makes HA impossible. It seems to me that we have to do the following:
1) configure complimentary equipment such as routers, to not be so picky. is this possible? a low-level ethernet device like a router/switch needs to map ethernet hardware mac addresses to IP addresses.
2) design each piece of equipment in the HA environment to be HA-aware. no more plugging in devices one by one. that requires a paradigm switch between the object-oriented to the relationship-oriented. it's no longer primarily all about boxes and addresses -- it's about how they relate -- who's responsible for who.
3) i dont know! point me to where I can read about HA theory, and what's been tried, and who else is in the game. i've built linux software RAIDs and i'm on linux-raid@vger.rutgers.edu.
On Thu, 10 Sep 1998, Steve Gremban wrote:
As already stated, for the "live" server to take over it would have to have an interface with both the IP address and MAC address changed and the NVRAM state copied. But also, I don't think that the NFS filehandles for the "live" filesystem would match the "dead" filesystem and you would get stale filehandles so this would only work if you were sharing the same filesystem between the two systems (which is what the new Netapp failover solution does).
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