[horde] IMP IMAP DB Cache backend lifetime

[Jens Wahnes]

Joao S Veiga wrote:
> There is a "NOT RECOMMENDED" for sql in the "Horde Cache" configuration 
> option; is that what you mean?

Yes.

> But we're talking about the "IMP IMAP Cache", which can use the "Horde 
> Cache" (not recommended), or hashtable/nosql/sql (recommended) according 
> to imp/backends.php:

You are right, of course, in the sense that that the comments in 
.../imp/backends.php do not explicitly discourage using the "sql" 
backend for IMAP caching. However, using a relational database server 
for purposes of caching is really not a good idea, except for very small 
installations where you don't want to run any other service (like Arjen 
pointed out). The same reasons apply for IMAP caching that rule out 
"sql" as a backend for Horde Cache.

Relational databases take many extra steps to make sure that data 
commited to the server is available, consistent, and saved on disk no 
matter what.  For cached data, which can easily be restored from another 
source, it does not make sense to take these extra steps. Cached data is 
just not valueable enough to be stored in a relational database on a 
larger scale. When you do put invalueable data into your relational 
database server, this can easily backfire when you have many users, 
since the amount of changes that any relational database server can 
handle is limited.


Jens

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