Re: Replicated hosts in autofs

[Mike Waychison <Michael.Waychison@Sun.COM>]

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raven@themaw.net wrote:
> On Fri, 12 Nov 2004, Keeler, Wayne T (Wayne) wrote:
> 
> 
>>Hi,
>>
>>I have read many threads regarding replicated hosts for autofs v3 and
>>v4. 
>>
>>Here is my scenario:
>>
>>On a linux host (Opteron running RHEL 3 WS kernel 2.4.21-20.ELsmp, I
>>have the following automount configured:
>>
>>mountpoint -fstype=nfs,-proto=tcp,ro host1,host2:/tmp/ro
>>
>>The goal in my implementation is that after the initial mount occurs to
>>host1 or host2, if that particular host fails, nfs will pick up the
>>mount on the alternate host. Note that since both mount points are read
>>only, this serves as a lower cost, higher availability solution. This
>>works on Solaris.
> 
> 
> Nop. Not available in Linux.
> 
> 
>>I have had no success with this on Linux. It seems that the replication
>>only works on the initial mount/rpc call. Once the initial mount occurs,
>>it doesn't appear there is any fail-over capability.
> 
> 
> Yep. I believe you are correct.
> 
> 
>>I have even installed RedHat's Beta version of E4 (kernel
>>2.6.9-1.648_ELsmp). The result is the same. If I crash the machine that
>>originally had the mount-point, the end result is a hung mount and
>>fail-over never occurs.
>>
>>I can't seem to find any information that indicates that this should or
>>should not work by design.
>>
>>Can someone please definitively tell me if the capability I am seeking
>>is available via the autofs supplied by RedHat in Enterprise 3?
> 
> 
> I don't think that this is practicle to do in autofs.
> 
> This is the source of statements like "this functionality belongs in NFS 
> or mount". The limited implementation in autofs is there because of the 
> lack of it in NFS.
> 
> The question then is "does autofs or mount/NFS handle this in Solaris"?
> 
> Mike?

This is handled in the NFS code in Solaris (for the read-only failover
bits).  I remember reading it being listed on one of the many Linux nfs
priority lists on the net, but I can't find it now.  I don't think
anyone is working on this just yet.

- --
Mike Waychison
Sun Microsystems, Inc.
1 (650) 352-5299 voice
1 (416) 202-8336 voice

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