Re: DB mail
At 10:44 PM 9/22/2006 +0200, Jordi Miguel wrote:
>I'm not agree with that. Although queries can be very efficient this
>dosen't avoid to parse the filesystem later to locate the data on the
>disk.
I guess the main rationale for an SQL based mail system is that it can be a
higher performance file system on top of the volume's file system. The
judgment call is whether this trade off is worth it. Seeks under a database
should be faster than seeks under the file system. This is because the
database is a monolithic file and there is no directory searching involved.
The seek time of the database is basically going to be the time to throw the
disk's read head. Over time however this paradigm can break down.
Databases with variable length rows are just as susceptible to fragmentation
as any file system. The solution is to optimize ur tables on a regular
basis. This effectivly degragments the table (intra-file). I'm not aware
of any Linux file system defraggers although I'm sure something's out there.
The judgment call here is which is better? If u have to dismount the volume
to defrag then the database wins. No downtime with the database if u do it
right. The other advantage of a database is u have the power of SQL. U
just can't manipulate maildir files with the ease with which u can
manipulate a database (DBA speaking here ;). Another advantage of a
database is that u can have n-level redundancy with clustering. Once u have
ur base system running u can scale up ad infinitum and still have that handy
SQL interface. U can have n number of MTA/MDA's running simultaneously.
Need more load? Just clone up a new server and bam, ur done. SQL takes
care of the nitty gritty transparently. On the maildir side u could
probably do something similar with AFS or GRFS(?). The downside to the
database is that SQL can be intimidating if ur not familiar with it. It
wasn't designed to be a file system. It was designed to be a relational
cross referencing thingy. To get the true power out of it u really need to
know what ur doing. So the maildir scheme wins for out-of-the-box ease of
use. I've done several database projects and I just love what u can do with
SQL. If I were writing an MTA/MDA I would do it with SQL. In the end its a
personal preference thing. How much do u know, how much do u care, how far
do u want to take it, do u want tried and true or push the envelope, etc.
I'm not endorsing any product. I haven't even looked at an SQL MDA/etc.
Actually for my lowly purposes Postfix and procmail are good enough.
--
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