[Dovecot] NFS random redirects

[Timo Sirainen]

On Oct 20, 2009, at 4:47 AM, Thomas Hummel wrote:

>> If you do it, you'll most likely see some random index related  
>> errors.
>
> But are index related errors recoverable (does dovecot notice and  
> fix it
> dynamically ?) or will they cause client-side corruption ?
>
> How bad would that corruption be ? (like fetching wrong message,  
> since index
> store nextuid as well ? setting wrong flag ? ...) and how could a  
> client fix it ?

It's unlikely that anything bad happens, but who knows. Random  
unnoticed corruption can do pretty much anything.

>> caches.. So I've added some highly OS-specific code that works most  
>> of
>> the time, but not perfectly. It works best with Linux.
>
> Ouch! I run dovecot on FreeBSD ;-(

FreeBSD's NFS seems to be among the worst..

>> imaptest exists now in http://imapwiki.org/ImapTest
>
> Thanks. Sorry I didn't find it. Do you have any suggestion to test  
> specifically
> nfs corruption chances ?

Not really. Just running the stress test on the same mailbox in 2+ NFS  
clients should start showing the problems somewhat soon if they are any.

>> Actual mail content should be safe. Unless you just happen to get  
>> such
>> a cache file corruption that Dovecot doesn't notice it and sends some
>> broken headers to IMAP client.
>
> If that happened, with Maildir, the actual content on disk on server  
> wouldn't
> be corrupted I guess,

Right.

> so I would that be recoverable on the client ?

If anything else fails, clearing client caches (or recreating the  
account on client side) should work, yes.