On Sun, Nov 23, 2008 at 5:28 PM, Glen Eustace <geustace@godzone.net.nz> wrote:
> Hi all,
>
> I was wondering whether anyone has had any experience running postgresql in
> a vm under ESx. VMware provides significant HA/DR oppurtunities and we
> would like to use it if we can. The DBase would be on a EMC SAN hosted LUN
> and the ESx servers would be dual Quad CPU HP DL-380/G5s. At this stage we
> would use iSCSI for SAN connectivity as our testing with MS-SQL has not
> indicated that FC is needed.
>
> We are getting a bit of push back from the external support agency who seem
> more than a little bit nervous about the environment. I would appreciate
> any comments.
Generally speaking, virtualization allows you to take a bunch of low
powered servers and make them live in one big box saving money on
electricity and management. Generally speaking, database sers are big
powerful boxes with lots of hard disks and gigs upon gigs of ram to
handle terabytes of data. Those two things seem at odds to me.
When I saw you post that the ESx servers would be dual quad core
machines I immediately thought how nice that would be to run pgsql on,
without vmware between it and the hardware.
On to the real issue. PostgreSQL, like any database, requires certain
guarantees about the data it's writing to the disks actually being
written when the OS says it was. With a SAN and vmware, you now have
a few extra layers that could like to your database. In order to see
if things are working properly, you need to do some semi-destructive
testing. Meaning you need to start up a few hundred clients running
read/write transactions, force a checkpoint, and pull the plug on
various parts (or all) of your system and see if it can come back up.
Do not trust UPSes, generators, power conditioners etc. They can and
do ALL fail sometimes. I've seen it happen a few times myself, when
systems that could not possibly lose power lost power. If your system
can't guarantee data integrity in case of power loss then I would push
back on it too.
What, exactly, as you looking to gain by running pgsql under vmware on
such hardware?