[asterisk-users] Recommendations for IMAP Voicemail

[Gareth Blades]

With regard to your question about the imap store I highly suspect that 
if it is unavailable when the message is saved then the message will be 
lost. There are configuration options for the timeout and it might retry 
a couple of times but Asterisk has no scheduling so I cannot see a way 
for it to record the fact that there are voicemails waiting to be uploaded.

You are concerned about reliability but this is not an easy thing to 
fully plan for. You could have a couple of asterisk boxes with config 
stored in a database which is replicated between two of them. For 
voicemail and general audio storage this could be on a NAS which 
replicates data over to a backup. However if the primary NAS fails then 
because you are using NFS this has a tendancy to hang which will cause 
problems.
You could use IMAP for storage but you are pushing the file storage 
issues just furthur away. If you use an IMAP store based on MAILDIR++ 
then you can have multiple IMAP servers mounting the same data and it 
will work fine however this approach typically has a poor performance 
when it comes to stat files in a mailbox so if you have lots of 
voicemails asterisk will pause a long time. Other systems such as Cyrus 
which use a database are much faster (sometimes 100 times faster!) but 
much slower when it comes to storing new files.

We have a redundant pair of opensips servers performing load balancing 
between multiple asterisk boxes which have a large gluster file storage 
mounted on each. Thats a large number of machines but is the sort of 
topology you need for something to be fully fault tolerant.


On 06/05/15 15:15, Olivier wrote:
> imapsync seems a very interesting tool.
> Thanks for sharing this.
>
> Now I'm still curious to learn if moving from local file storage to 
> cloud IMAP storage is still resilient to short network outages 
> (without IMAP replication).
>
> Regards
>
> 2015-05-06 10:18 GMT+02:00 Gareth Blades 
> <mailinglist+asterisk at dns99.co.uk 
> <mailto:mailinglist+asterisk at dns99.co.uk>>:
>
>     On 05/05/15 17:52, Olivier wrote:
>
>         2. From personal experience, would you rate an IMAP migration
>         as an easy or as a difficult task ?
>         By IMAP migration, I mean changing from one IMAP software to
>         another, on the same or on an other box.
>
>
>     There is software called 'imapsync' which will sync mail from one
>     imap store over to another. I have used that to migrate from one
>     server to another and it was pretty painless. It took a while to
>     do but it does it a mail at a time so it is something you can run
>     while everyone is using the system and then right at the end you
>     just need to do a final sync while voicemail is disabled.
>
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