Re: 2 questions

Thanks for the info Scott.

Can I setup a primary server called A that uses the Postgres installation
on a nfs mounted filesystem and then A does a daily backup of database A
and restores to database B on same filesystem.

Then I have server B acting as cold standby and if server A goes down, then
B would make the backup DB active?

In this case, both server A and B have the same NFS mount, but B is not
always writing to the data.

The target environment I am moving to is a RAID5 system with mirrored
discs. I will be getting a VM on a physical server and the mirrored disks
will store the database. I would like to setup a primary and secondary as
cold standby.

I am fairly new to PG so asking these questions.

Please advise. Thank you.

On Tue, Dec 1, 2015 at 11:26 AM, Scott Mead <scottm(at)openscg(dot)com> wrote:

>
>
> On Nov 30, 2015, at 12:54, anj patnaik <patna73(at)gmail(dot)com> wrote:
>
> 1) directory listing:
>
> /opt/nfsDir/postgres/9.4/
> /bin
> /data
> /etc
> /pgAdmin3
> ....
>
>
> The data directory will cause you many problems. You will need one data
> directory that is accessed by one AND ONLY one host for each node
> connected. You can't run an instance on multiple machines pointing to the
> same 'data' directory simultaneously. Data directories cannot be shared by
> multiple instances simultaneously, that's an active/active shared disk
> cluster and most databases don't support it or require massive overhead (
> network/licensing I.e. Oracle rac) to do that.
>
> You *can* re-use the other directories, it can be wrought with issues,
> and you need to carefully think though upgrades, etc....
>
> 2) The way I am using PG now is that I have specified the directory above
> as the location to install it (from graphical installer).
>
> Now, it appears that postgres places files in other directories besides
> the one specified in the installer. For instance, there are scripts in
> /etc/init.d to start the service.
>
> So in answering my own question: it appears PG places files in other dirs
> so when I am given a new VM/different physical server with the same NFS
> mount I would either need to copy these files over or better yet un-install
> the current PG and re-install from scratch.
>
> Thanks,
> ap
>
> On Fri, Nov 27, 2015 at 8:30 PM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
> wrote:
>
>> On 11/27/2015 01:17 PM, anj patnaik wrote:
>>
>>> Hello,
>>> Yes, postgres is currently installed on a nfs mounted file system. So
>>> when graphical installer runs, there is a form which asks location for
>>> installation. I specified this path /opt/nfsDir/Postgres where nfsDir is
>>> a nfs mount. So currently this is where PG 9.4 lives.
>>>
>>
>> What is under /opt/nfsDir/Postgres?
>>
>>
>>> My question is when I am given a brand new VM on a different physical
>>> server, can I mount that same NFS FS and use the Postgres or do I need
>>> to re-install PG on new VM?
>>>
>>
>> How are you using Postgres now? Please be specific, more detail is better
>> then less at this point.
>>
>>
>>> I am not sure if PG writes to any other directories besides the one
>>> where it is installed.
>>>
>>
>>
>>
>>> On the issue of logging, I see a lot of log statements because client
>>> apps do upserts and since I use Tcl I don't have a SQL proc, but rather
>>> I let it exception and then do an update on the row.
>>>
>>
>> You can Tcl in the database:
>>
>> http://www.postgresql.org/docs/9.4/interactive/pltcl.html
>>
>> That will not change things if you let the database throw an exception
>> there also.
>>
>>
>>
>>> So, you can limit the size of an individual log, but there is no way to
>>> tell PG to keep the log file short?
>>>
>>> if i choose FATAL, I'd lose some log, right?
>>>
>>> Thank you!
>>> ap
>>>
>>>
>> --
>> Adrian Klaver
>> adrian(dot)klaver(at)aklaver(dot)com
>>
>
>