[rt-users] Migrating from Postgres to MySQL

Kage kagekonjou at gmail.com
Tue Jul 28 16:12:55 EDT 2009

(didn't do a reply-all, sorry if you get this twice, Ken)

What, if any, performance gains exist by using an NFS mountpoint for
the Postgres database within a virtual machine?  In this case, I/O is
not directly placed on the virtual disk (unless the actual "act" of
I/O itself, regardless of what is being acted upon (virtual disk or
not), is also an issue).  Could this potentially yield any performance

Also, no, I have not tried MySQL yet with our RT setup.  I'd like to
move our database to MySQL to do some testing with that and gather
realistic metrics of "here's our data in Postgres vs. MySQL".

On Tue, Jul 28, 2009 at 3:51 PM, Kenneth Marshall<ktm at rice.edu> wrote:
> On Tue, Jul 28, 2009 at 03:35:12PM -0400, Kage wrote:
>> Well, basically, Postgres is seemingly a bucket of fail specifically
>> for the RT system I maintain.  We run RT/Postgres on a Ubuntu Hardy
>> LTS virtual machine running 2 virtual CPUs and the KVM maximum of 2GB
>> RAM, but Postgres ends up using so much in resources that it actually
>> kills the entire KVM system on the virtual host.  I know tuning of
>> Postgres can fix this, but we've experienced issues with Postgres on
>> many other virtual machines, leading us to believe that it may simply
>> be an issue with Postgres not getting along well with KVM (which is a
>> somewhat known issue).  Ideally, I want to migrate my RT database from
>> Postgres to MySQL, and preserve ALL data (tickets, attachments, links,
>> everything).  Is there an "guaranteed to work" method to do this that
>> anyone knows of?  Thanks!
>> Specs:
>> Postgres: 8.3
>> RT: 3.6.5
>> MySQL candidate on Hardy: 5.0.51a-3ubuntu5.4
>> Any help would be greatly appreciated.  Thanks!
>> --
>> ~ Kage
>> http://vitund.com
>> http://hackthissite.org
> Hi Kage,
> I have had trouble with VMs with any I/O bound system. Have you
> tested your system with MySQL? You may just be swapping one I/O
> problem for another. That being said, for anything but the most
> trivial of DBs, tuning your backend DB be it PostgreSQL, MySQL,
> Oracle,... is critical for getting good performance.
> Another data point, I have had a simple repeated file read of a
> DNS zone file for an XFER tank a VM. VMs work well for CPU intensive
> tasks with small amount of I/O. For any larger amount of I/O, using
> real storage is a must. Good luck with whichever backend you choose.
> A big plus for both the Oracle and PostgreSQL backend is the
> availability of full-text indexing which allows content and attachment
> searches to use an index and not take your DB with a full table scan.
> Regards,
> Ken

~ Kage

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