Re: Humor me: Postgresql vs. MySql (esp. licensing)

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: Shridhar Daithankar <shridhar_daithankar(at)persistent(dot)co(dot)in>
Cc: <nolan(at)celery(dot)tssi(dot)com>, <pgsql-general(at)postgresql(dot)org>
Subject: Re: Humor me: Postgresql vs. MySql (esp. licensing)
Date: 2003-10-09 13:42:00
Message-ID: Pine.LNX.4.33.0310090739190.15891-100000@css120.ihs.com
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On Thu, 9 Oct 2003, Shridhar Daithankar wrote:

> nolan(at)celery(dot)tssi(dot)com wrote:
>
> >>One of my friend lost data with mysql yesterday.. The machine was taken down for
> >>disk upgrade and mysql apperantly did not commit the last insert.. OK he was
> >>using myisam but still..:-)
> >
> >
> > It sounds like that is more a problem with improper operating protocols
> > than with the underlying database.
>
> No. Problem is machine was shutdown with shutdown -h. It sends sigterm to
> everybody. A good process would flsuh the buffers to disk before finishing.
> Mysql didn't on that occasion.
>
> Transactions or not, this behaviour is unacceptable for any serious app.
>
> >
> > Would PG know enough to do a commit regardless of how the database was
> > shut down? A second question is whether doing a commit is what the user
> > or application would always want to have happen, as it could result in a
> > half-completed transaction.
>
> Do a shutdown -h on a live database machine with pg. It will gracefully shut
> itself down.

If you're running on a properly setup machine (i.e. SCSI and / or battery
backed RAID cache) you can just pull the plug and pg will restart
gracefully. It's one of the standard tests.

Try this on a SCSI based machine with a journaling file system:

pgbench -i -s 10
pgbench -c 200 -t 1000000
wait a minute
start a vacuum
pull the plug
wait a minute
plug it in (turn it on if necessary)
voila, postgresql will recover gracefully with no corruption.

Now ask the consultant to do the same for MySQL. :-)

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