Re: Table Partitioning in Postgres: - Mailing list pgsql-general

From Jonathan Bartlett
Subject Re: Table Partitioning in Postgres:
Date
Msg-id Pine.GSU.4.44.0302190341080.17668-100000@eskimo.com
Whole thread Raw
In response to Re: Table Partitioning in Postgres:  ("Shridhar Daithankar<shridhar_daithankar@persistent.co.in>" <shridhar_daithankar@persistent.co.in>)
Responses Re: Table Partitioning in Postgres:  (Greg Copeland <greg@CopelandConsulting.Net>)
List pgsql-general
> Certainly. But the advantage will not be visible unless you put it on a disk
> that is on separate IDE or SCSI channel. Now that you have a large database,
> are you using more than one SCSI channel? Otherwise just putting on different
> disks will not help as much.

This is quite untrue.  Even going over a single channel, it is highly
unlikely that a single disk or RAID set is going to saturate the channel,
because of disk seek times.  The purpose of putting tables on different
disks than the indexes is so that the disks don't have to keep seeking
back-and-forth between table, index, table, index, table, index, etc.
Likewise with transaction logs, if they have their own disk, the
read/write heads can pretty much stay in the same place with transaaction
log updates.  Using these benefits you are more likely to make full use of
a single channel than otherwise.

Jon


>
>
> > Even Postgresql has to be told to perform vaccum and analyze.
> > If the OS had enough intelligence we could trust it to do a good job,
> > but until then ...
>
> Partially true. Postgresql could have done vacuum at runtime at the cost od
> performance. So developers delegated the task to admin.
>
> Looking for a solution in problem, the real benefits won't be visible unless
> you put it on a different disk channel. Otherwise RAID is your best bait now
> as OS can handle it intelligently and it enhances the IO bandwidth immensely.
>
> Other than that you can not do much with postgresql right now.
>
>  Shridhar
>
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