Hi,

Can i create create a cluster of postgresql server by sharing the
database file on a SAN? I am also looking into slony but slony replicate
data to each server and my database will potentially have terabytes of
data. I am thinking about a solution where a cluster of database server
will share database files on SAN, can this be done? I am also looking
for a load balancing salution for the postgresql database. Any sugestion?



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robertngo@perridot.com (Robert Ngo) writes:
> Can i create create a cluster of postgresql server by sharing the
> database file on a SAN? I am also looking into slony but slony replicate
> data to each server and my database will potentially have terabytes of
> data. I am thinking about a solution where a cluster of database server
> will share database files on SAN, can this be done? I am also looking
> for a load balancing salution for the postgresql database. Any sugestion?

What you wish can NOT be done.

There can only be ONE postmaster for each database cluster; you can
NOT have multiple servers sharing a single cluster.
--
(reverse (concatenate 'string "gro.gultn" "@" "enworbbc"))
http://cbbrowne.com/info/internet.html
"The real romance is out ahead and yet to come. The computer
revolution hasn't started yet. Don't be misled by the enormous flow of
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adaptations of incomplete ideas." -- Alan Kay

Robert Ngo wrote:

> Chris Browne wrote:
>
>> robertngo@perridot.com (Robert Ngo) writes:
>>
>>
>>> Can i create create a cluster of postgresql server by sharing the
>>> database file on a SAN? I am also looking into slony but slony
>>> replicate
>>> data to each server and my database will potentially have terabytes of
>>> data. I am thinking about a solution where a cluster of database server
>>> will share database files on SAN, can this be done? I am also looking
>>> for a load balancing salution for the postgresql database. Any
>>> sugestion?
>>>
>>
>>
>> What you wish can NOT be done.
>>
>> There can only be ONE postmaster for each database cluster; you can
>> NOT have multiple servers sharing a single cluster.
>>
>>
> so there is no ways for the file storage to be shared between postgres
> cluster? Then i will need to add a huge amount of storage every time
> new server is added.
>
Is there any way i can reduce the storage requirement of the database
server cluster?

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TIP 5: don't forget to increase your free space map settings

robertngo@perridot.com (Robert Ngo) writes:

> Robert Ngo wrote:
>
>> Chris Browne wrote:
>>
>>> robertngo@perridot.com (Robert Ngo) writes:
>>>
>>>
>>>> Can i create create a cluster of postgresql server by sharing the
>>>> database file on a SAN? I am also looking into slony but slony
>>>> replicate
>>>> data to each server and my database will potentially have terabytes of
>>>> data. I am thinking about a solution where a cluster of database server
>>>> will share database files on SAN, can this be done? I am also looking
>>>> for a load balancing salution for the postgresql database. Any
>>>> sugestion?
>>>>
>>>
>>>
>>> What you wish can NOT be done.
>>>
>>> There can only be ONE postmaster for each database cluster; you can
>>> NOT have multiple servers sharing a single cluster.
>>>
>> so there is no ways for the file storage to be shared between
>> postgres cluster? Then i will need to add a huge amount of storage
>> every time new server is added.
>>
> Is there any way i can reduce the storage requirement of the database
> server cluster?

Well, the base amount of storage for each instance is only about 26MB.

sh-3.00$ /opt/OXRS/dbs/pgsql8/bin/initdb -D .
Success. You can now start the database server using:

/opt/OXRS/dbs/pgsql8/bin/postmaster -D .
or
/opt/OXRS/dbs/pgsql8/bin/pg_ctl -D . -l logfile start

sh-3.00$ du
176 ./global
4 ./pg_xlog/archive_status
16412 ./pg_xlog
12 ./pg_clog
12 ./pg_subtrans
4640 ./base/1
4704 ./base/17229
9348 ./base
4 ./pg_tblspc
25992 .
sh-3.00$

For any sort of interesting-sized database, this bit of overhead,
which is mostly WAL files, doesn't strike me as being terribly
material. I can't see 26MB being considered "huge" in a SAN context.

You only need additional storage (beyond that) when your applications
are actually requesting to store data. There is no magical way to
avoid that need for additional storage.
--
let name="cbbrowne" and tld="acm.org" in name ^ "@" ^ tld;;
http://cbbrowne.com/info/languages.html
"The newsreader abuse likely stems from more fundamental, than merely
just the UI, design disagreements. Requests from Unix programmers to
replicate Free Agent rightfully so should trigger the throwing of
sharp heavy objects at the requesting party."
-- jedi@dementia.mishnet (jedi)

Robert Ngo wrote:

> Robert Ngo wrote:
>
>> Chris Browne wrote:
>>
>>> robertngo@perridot.com (Robert Ngo) writes:
>>>
>>>
>>>> Can i create create a cluster of postgresql server by sharing the
>>>> database file on a SAN? I am also looking into slony but slony
>>>> replicate
>>>> data to each server and my database will potentially have terabytes of
>>>> data. I am thinking about a solution where a cluster of database
>>>> server
>>>> will share database files on SAN, can this be done? I am also looking
>>>> for a load balancing salution for the postgresql database. Any
>>>> sugestion?
>>>>
>>>
>>>
>>>
>>> What you wish can NOT be done.
>>>
>>> There can only be ONE postmaster for each database cluster; you can
>>> NOT have multiple servers sharing a single cluster.
>>>
>>>
>> so there is no ways for the file storage to be shared between
>> postgres cluster? Then i will need to add a huge amount of storage
>> every time new server is added.
>>
> Is there any way i can reduce the storage requirement of the database
> server cluster?

Maybe you can provide us with more information on your environment,
application, expected load, etc. so we can help you explore other
possibilities.
Best Wishes,
Chris Travers


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TIP 9: In versions below 8.0, the planner will ignore your desire to
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