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Re: improve performance

From: Tom Samplonius <tom(at)sdf(dot)com>
To: Alexaki Sofia <alexaki(at)ics(dot)forth(dot)gr>
Cc: pgsql-sql(at)postgresql(dot)org, pgsql-interfaces(at)postgresql(dot)org
Subject: Re: improve performance
Date: 2001-01-15 16:37:23
Message-ID: Pine.BSF.4.05.10101150831420.22851-100000@misery.sdf.com (view raw or flat)
Thread:
Lists: pgsql-interfacespgsql-sql
On Mon, 15 Jan 2001, Alexaki Sofia wrote:

> Hello,
> 
> A)
> I am going to load a huge amount of data in the DBMS using JDBC 
> and I want to reduce as much as possible the required loading time. 
> 
> Initially I loaded all data in one transaction. Subsequently, I increased
> the number of buffers and disabled fsync() (-o -F) and I loaded the
> data again but the performance was almost unchanged. Does it make sense??

  Yes.  Syncing is only done at the end of a transaction.  The difference
between one fsync() and none is not measurable.

  Large amounts of buffers helps in read performance, not write
performance.

> How can I improve performance?  To note that no indexes are created on the 
> tables and that I load both "insert into" and "create table" statements.
> ------------------------------
> B)
> I want to reduce the space (8 Kb) allocated by 
> DBMS when more space is required to load the data in a table. I reduced
> the parameter BLCKSZ but the space allocated remains the same, that is 8
> KB. 
> How can the allocated space be reduced? If the space was reduced  
> would loading time and query time increase?

  No.  Reducing the blocksize does not sound like a good idea.  Why would
you want to reduce the amount of allocated space?  I actually wish that
Postgres would preallocate a lot of blocks in advance (ie. 100 x 8KB).
That would probably improve performance, as it would not have to keep
re-extending the file.


  The best way to improve write performance, is to get faster disks
connecting to a fast interface.  Also, get lots of disks (4 to 6).  Pair
them into RAID1 sets, then strip over them.  Use a RAID controler with a
battery backed cache in write-back (write cache) mode.

> Thank you in advance for your help
> Sofia Alexaki


Tom


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