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From:Michael Widenius Date:April 18 1999 9:12pm
Subject:Multiuser/multideamon and CPU/RAM/DISK usage
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>>>>> "Martin" == Martin Lorensen <mlo@stripped> writes:

Martin> Hi!
Martin> Background:
Martin> ^^^^^^^^^^^
Martin> We are planing to set up a MySQL server on one of our unix-webhosting
Martin> servers. The plane is that all users will be offerd to get their own
Martin> database for their website using PHP.

Martin> Our concern is wheter to have a single MySQL deamon or a MySQL deamon for
Martin> each website (running with seperate uid's, log- and database-path etc.).

Martin> Safety is somewhat the same - Both setups have problems. Administration is
Martin> fare easiest with one deamon - as far as I can see.

Martin> Our primar concern is, if we will be able to see what is going on if the
Martin> CPU/RAM/DISK load is raising dramaticly or if we see denial-of-service
Martin> attacs.

Martin> Problem!
Martin> ^^^^^^^^
Martin> E.g. two users has active websites which simular queries, but one has set
Martin> up a index on the queried key, the other doesn't - Or the databases has
Martin> siginificantly diffrent size - Will we then be able to see which of the
Martin> users that is causing the problem?

Martin> Having only on deamon, that deamon will take up all the CPU-time, require
Martin> more RAM, and constantly in an I/O-wait state.

Martin> Having multible deamons, the deamon owned by the user causing trouble,
Martin> will have abover symptoms, the rest of the deamons runs as normal - It
Martin> would be easy to stop/debug the problem.

Martin> Question?
Martin> ^^^^^^^^^
Martin> Is there anywhere in the log (or some place else) we could find that
Martin> information if we are running only one deamon? Is there a "debug" flag or
Martin> something that will enable us to do so?

Martin> Thanks in advance!

Martin> Martin Lorensen
Martin> Tele2 A/S


You can with 'mysqladmin processlist' check which users are running what type 
of queries and how long they have executed.  You can't however check
how much CPU/RAM a given user has used.

It would be trivial to add logging of how long each query took, but
RAM usage per query is a much harder and CPU usage is almost

We at TCX only use one MySQL daemon to handle all queries from
different customers against their own databases and for us this
haven't caused any problems.  (We have on the other hand educate our
SQL users so they should know what they are doing :)

If you have no control over your users, multiple daemons would
probably be the easiest choice.  The nice part with this is that you
can easily restrict the number of simultaneous connection for each 

MySQL should also run relatively well even if you run it with VERY small

Multiuser/multideamon and CPU/RAM/DISK usageMartin Lorensen18 Apr
  • Multiuser/multideamon and CPU/RAM/DISK usageMichael Widenius19 Apr