[Cluster-devel] Re: [NFS] [PATCH 0/4 Revised] NLM - lock failover

[Wendy Cheng <wcheng@redhat.com>]

Wendy Cheng wrote:
> Marc Eshel wrote:
>>> The detailed overall steps were described in the first email we sent 
>>> *long* time (> 6 months, I think) ago. The first step of the whole 
>>> process is tearing down the floating IP from the failover server. 
>>> The IP is not accessible until filesystem is safely fail-over and 
>>> SM_NOTIFY ready to be sent.
>>
>> I thought this is a solution for an active active server where a 
>> cluster file system can export the same file system from multiple NFS 
>> servers.
>> Marc.
>>
>
> Yes ... but remember we should have two cases here:
>
> 1) Local filesystems such as ext3 - both IP and filesystem are not 
> accessible during the transition.
> 2) Cluster filesystem such as GFS or GPFS - filesystem may still be 
> accessible (depending on the configuration, say you have advertised 
> two exported IP addresses, each serving different subdirectories for 
> the very same cluster filesystem). The failover IP should be suspended 
> during the transition until SM_NOTIFY is ready to go out (but the 
> other IP should be up and services the requests as it should).
>
> I assume people understand that the affected export entries should 
> have been un-exported (as part of the over-all process).

To remind people, we had described the overall steps in the first round 
of kernel interface discussions submitted to nfs mailing list (before 
implemented the code). These steps included un-export the entries, 
tearing down the IP, filesystem migration, SM_NOTIFY, grace period, etc. 
I'm in the middle of redoing the write-up. It will be uploaded into 
somewhere soon.

-- Wendy