[Dovecot] cannot update mailbox - unable to lock for exclusive access

[Stan Hoeppner]

On 11/26/2012 1:58 PM, 1st WebDesigns wrote:
> 
>> So this is a step in the right direction.  But still far less than
>> optimal.  The read/write lock contention on mbox is unnecessarily eating
>> up system resources (mainly memory), and causing unnecessary delivery
>> delays to the mailbox.  You should really start looking at migrating to
>> maildir.  It's not that difficult (though maybe more so with 1.0.7) if
>> you don't have a ton of mailboxes, and especially with POP since the
>> mailboxes typically wont be holding much mail to migrate.  How many do
>> you have?
> 
> There's around four hundred mail boxes or so.  Some used more
> intensively than others.

There are methods to convert one mailbox at a time, groups of mailboxes,
or all mailboxes in one fell swoop in a batch mode.  I'm uncertain WRT
the status of the tools in 1.0.7, but given the age of that release you
may avoid problems by upgrading to Dovecot 1.2.x or later before doing
the conversion.  If you attempt the conversion on 1.0.7 and hit snags,
this mailing list may not be of much help as nobody has used 1.0.7 for
years.  You may want to post a new thread asking Timo about such a
conversion with 1.0.7.  He doesn't seem to be paying attention to this
thread.

>>> Our server is with Rackspace, and RHEL5 is the OS they offered us as an
>>> upgrade path from RHEL4.  So they're getting the support from Red Hat
>>> and we're getting the support from Rackspace.
>>
>> The plot thickens again.  You're using a rented server.  Sigh...
>>
>> This entire thread could have been greatly shortened, saving all of us
>> much time, if you'd have given all these details up front.
>>
>> Is this a cloud server (shared host), or a dedicated server?
> 
> It's a dedicated server
> 
>>
>> FWIW, you don't have RHEL5, but CentOS 5.  Hosting companies don't pay
>> for RHEL licenses for 10s of thousands of hosts.
> 
> It's RHEL5:
> 
> $cat /etc/issue
> Red Hat Enterprise Linux Server release 5.8 (Tikanga)
> 
> The cost of the license is included in our contract.

Now that's interesting.

>>
>> I have a few salient recommendations for you:
>>
>> 1.  Migrate to maildir.  It is far more appropriate for a POP workload.
> 
> Yes, this will be our next course of action
> 
>> 2.  Switch to a hosting provider that offers much more recent software.
> 
> We can upgrade the software if we wish, but will no longer get full
> support from Rackspace if we do this.

And you consider this a net loss?  If you're that dependent on your
provider's tit, find one that can suckle you on RHEL 6.3.  Or buy your
copy/license directly from Red Hat and get support directly from them.

>> 3.  Or, get a colo server so you can use whatever software you wish.
> 
> We can install whatever software we wish at the moment, but see the
> point above.

See my point above.  And WRT Dovecot and most other application
software, you'll get better support from the community than your bulk
hosting provider anyway.  Their primary business is making $$ from
providing you a host and a pipe.  Customer support is a cost, especially
application support, not a profit center, and thus is almost always a
secondary concern at best.  Red Hat's entire business model is customer
support, same for SuSE.

>> Finally, if this email service you're providing isn't all that critical
>> to you or your organization, simply prod along as you have been,
>> fighting these problems frequently along the way.
> 
> It's kind of working ok now but we will go with your recommendation of
> switching to maildir when we have time.  Thanks for your help

As I said, you can migrate users individually.  You could easily do 10
users a day during coffee breaks etc and be done in a month plus.  Do 40
a day and you're done in 10 days.  The only time you'll burn is in the
learning curve, not the actual mailbox migration which takes no time at
all with POP accounts.

Always test with a dummy mailbox first to iron out any issues.  Then
start migrating the problem users first, the smart phone users who tie
up their mailboxes for many minutes during download.

-- 
Stan