[Dovecot] Using a namespace for providing access to mail snapshots for user based on-demand restoration of email backups

[Tom Hendrikx]

On 05-04-12 17:28, Charles Marcus wrote:
> Hi all,
> 
> I'm planning on implementing this in my new upcoming dovecot instance,
> and would like to hear thoughts on how best to accomplish this. We will
> be paying Timo's support company to do the work, but obviously, the less
> work in the form of coding he has to do to get this working (I'm hoping
> it won't be a lot), the more money it will save us... ;)
> 
> First - I currently use rsnapshot to backup emails, so that is the
> use-case I'm most interested in getting working. It is rsync based, and
> like other rsync based backup programs it uses hardlinks to save storage
> space - so you can have a *lot* of backups (going back months, or even
> years), where each snapshot only adds a little more to the total disk
> space being used.
> 

<snip>

> What I'm envisioning is something like this...
> 
> 1. Define a namespace - for this example we'll call it 'Time Machine'
> 
> 2. Under this namespace, each user will see their, and *only* their
>    snapshots
> 
> So, each user would see something like this:
> 
> My Mail Account
>    Inbox
>    Drafts
>    Templates
>    Sent
>    Time Machine (sorted above user created folders if possible)
>     -4/3/12, 8:00am (first subfolder)
>        Inbox
>        Drafts
>        etc... (all other folders and sub-folders shown here)
>     +4/3/12, 12:00pm (first subfolder)
>     etc...
>    Other User Folders
>    ...
> 
> Or even better, I'm thinking some magical code that can group them by
> Date, like:
> 
>     -4/3/12 (first subfolder)
>        -8:00am (next sub-folder)
>           Inbox
>           Drafts
>           Etc... (all folders and sub-folders shown here)
>        +12:00pm
>        +4:00pm
>        +8:00pm
>     +4/4/12
>     etc...
> 
> Comments? Suggestions? Flames?
> 

The first interesting point I'd see with this, is that you supply the
mail client with a near endless supply of folders, which would take a
lot of caching space on the clients end, either (depending on the client
and its configuration) from the moment that you enable this fort hem, or
after someone starts searching in their 'time machine' for some old mail.

I see my mail client on a new install working quite hard to download
mail headers for 2 years of postfix/dovecot/etc mailing lists, so what
happens if you provide a 'time machine' namespace going 1 month back, 4
with snapshots a day (i.e. 31x4 =~ 120 times more headers to
download/index).

--
Tom