[Snort-users] Database performance question (MySQL or PostgreSQL?)

Kreimendahl, Chad J Chad.Kreimendahl at ...4716...
Fri Sep 26 08:26:08 EDT 2003


There is quite a bit of tuning that can be done to increase the
performance... However your problem likely lies in MySQL doing fulltable
scans for its JOINs.   You will probably be able to get it running
reasonably up to 200k records.   I would suggest, if this is NOT a
production system for a corporation,  that you delete all records within
a certain timeframe.

A query that deletes data from the other tables that subqueries for the
primary key (sid,cid) based on timestamp from the event table... Just
make sure you get the event table last..

Example for Oracle: (<days> = total number of days of data to chop off
the end)

DELETE FROM [table-to-delete-from (data, opt, iphdr, tcphdr, udphdr,
icmphdr, event)]
WHERE (sid,cid) IN
 (
   SELECT sid,cid FROM event WHERE event.timestamp <=
(min(event.timestamp)+<days>)
 )

Please note, that based on using the timestamp to delete records, this
is the only reliable way to make sure you're deleting the exact same
data.  Using the alternate that I've seen (NOW()-<days>), you're likely
to end up with events out there in other tables that aren't in event...
Or vice versa.

-----Original Message-----
From: Jyri Hovila [mailto:jyri.hovila at ...2940...] 
Sent: Friday, September 26, 2003 2:24 AM
To: snort-users at lists.sourceforge.net
Subject: [Snort-users] Database performance question (MySQL or
PostgreSQL?)


Howdy!

Please let's not let this turn this into SQL wars. =)

I'm sure this issue has been discussed several times before but I'm
unable to find anything about it in the snort-users archives.

I'm currently running several Snort sensors with a central MySQL
database. Recently the database speed has become a problem. When the
number of alerts is starting to reach 100 000, ACID is starting to get
slow. Add another 100 000 alerts and ACID is almost unusable.

My database server is not doing anything else but running MySQL and
ACID. Here are the specs:

- Pentium II 450 MHz (normally almost totally idle, jumps to 80% when
making SQL queries)

- 384 RAM (about 50% used, jumps to 60-70% when making queries)

- 7200 RPM IDE HD (yes, I know...)

As CPU and RAM utilization is almost never higher than 80% and still the
queries take awfully long to finish, could the HD be a problem?

I remember seeing discussions about differences between MySQL and
PostgreSQL performance. If I remember correctly, PostgreSQL was believed
to be somewhat faster. Could anybody with some real life experience on
this issue share hers/his knowledge?

Thanks!

- Jyri




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