Re: NFS and MIX ?

On 6/10/10 6:54 AM, Timo Sirainen wrote:
> On 10.6.2010, at 3.57, Andrew Daviel wrote:
>
>    
>> What are the chances of this working ? There would be no sharing of
>> files with any other NFS clients, just the one disk mount.
>>      
> With only one NFS client accessing the storage, it should work the same as a local disk, as long as you're using an NFS client that's not buggy (many Linux kernel versions are).
>
>    
That was my gut reaction too, but I'm not convinced it is the case. I 
also know that Mark would be better positioned to answer the question.

Yes, there's only one NFS server process, so things conceivably could be 
properly dealt with there. But having only one client host (IMAP server) 
isn't the same as only having one client process (as I understand it). 
Interactions of the NFS server with two NFS clients would seem to be the 
same whether those clients are on different hosts or are just different 
processes (eg, two imapds) on a single host. (One could imagine that in 
your case of a dedicated NFS mount, c-client could lock in /tmp on the 
local host for the NFS mounted files, but I don't know that this is 
done, or if it could be effective.)

See http://www.washington.edu/imap/documentation/locking.txt.html for 
Mark's documented handling (or not) of NFS. My reading of that is that 
imap-uw has no locking on mail files mounted via NFS.

I'll say that for normal file access (user files, not mail files) we 
used NFS mounted file systems for decades on Suns with no reports of 
mangled files. It was sure a shock years back when the first test we had 
of Linux NFS resulted in garbaged results. My instinct is still not to 
trust Linux NFS, though that may be unwarranted now.

>> How about other imap servers such as Dovecot ? Apparently it alleges it's NFS-safe, but one the posts here casts doubt on that.
>>      
> It's not perfect either with multiple NFS clients.
>
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>    

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