[Dovecot] what to expect from changing index location

[Davide Vaghetti]

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On 06/29/2011 06:36 PM, William Blunn wrote:
> On 28/06/2011 17:13, Davide Vaghetti wrote:
>> I have one thousand virtual users with mdbox mailbox format and 10 
>> GByte quota. I have noticed some performance problem related to
>> I/O (the mailbox disk is a 6TB raid1+0 on ISCSI), so I want to put
>> the index files on a different disk. My actual mail_location is:
>> 
>> mail_location = mdbox:/var/vmail/%-1.1u/%u/mdbox
>> 
>> and I want to switch to
>> 
>> mail_location = 
>> mdbox:/var/vmail/%-1.1u/%u/mdbox:INDEX=/var/indexes/%-1.1u/%u/
>> 
>> But I cannot figure out a pair of things:
>> 
>> - - do the switch trigger the rebuilding of the index files?
> 
> !!!!! DANGER, DANGER !!!!!!
> 
> Index files cannot be re-generated under mdbox
> 
> Go away and read http://wiki2.dovecot.org/MailboxFormat/dbox
> 
> "... with dbox the Index files actually contain significant data
> which is held nowhere else. Index files for both *single-dbox* and 
> *multi-dbox* contain message flags and keywords. For *multi-dbox*,
> the index file also contains the map_uids which link (via the "map
> index") to the actual message data. This data cannot be automatically
> recreated, so it is important that Index files are treated with the
> same care as message data files."
> 
> If you don't already know this, then you probably shouldn't even be 
> using mdbox.
> 
>> - - can I get rid of all the old index files?
> 
> NO!
> 
>> - - how much the index files (no fts squat) can grow?
> 
> First solve your understanding problem with mdbox, then worry about 
> details such as this.
> 


Bill, thanks for all the __important__ info. You almost saved my ass ;-)
 (BTW, that is why I was asking)

I'll check again the documentation to better understand index in the
mdbox context.

Nontheless, I still have to care about the index files grow factor, so
if you, or anyone else, can point me to the right documentation, or have
a rule of thumbs to know it, please share it.

Regards
davide


- -- 
Dott. Davide Vaghetti
Centro Servizi Informatici Facolta' di Ingegneria
Universita' di Pisa
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