Re: COPY into table too slow with index: now an I/O question

As a follow up to my own question:

I reran the COPY both ways (with the index and without) while running
iostat. The following values

are averages:

%user %nice %sys %iowait %idle

no index 39 0 2.8 11 47

index 16 1.5 2.1 34 46

I'm no performance guru, so please indulge a couple of silly questions:

1) Why is there so much idle time? I would think the CPU would either
be busy or waiting for IO.

2) It seems that I need to improve my disk situation. Would it help
to add another drive to my PC and

keep the input data on a separate drive from my pg tables? If so, some
pointers on the best way to set that up

would be appreciated.

Please let me know if anyone has additional ideas.

-----Original Message-----
From: pgsql-performance-owner(at)postgresql(dot)org
[mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of Rick Schumeyer
Sent: Thursday, December 01, 2005 12:58 PM
To: pgsql-performance(at)postgresql(dot)org
Subject: [PERFORM] COPY into table too slow with index

I'm running postgresql 8.1.0 with postgis 1.0.4 on a FC3 system, 3Ghz, 1 GB
memory.

I am using COPY to fill a table that contains one postgis geometry column.

With no geometry index, it takes about 45 seconds to COPY one file.

If I add a geometry index, this time degrades. It keeps getting worse as
more records are

added to the table. It was up to over three minutes per file on my most
recent test.

The problem is that each file contains about 5 - 10 minutes of data.
Eventually, I want to

add the data to the table in "real time". So the COPY needs to take less
time than

actually generating the data.

Here is the relevant section of my postgresql.conf.

# - Memory -

shared_buffers = 5000 # min 16 or max_connections*2, 8KB each

#temp_buffers = 1000 # min 100, 8KB each

#max_prepared_transactions = 5 # can be 0 or more

# note: increasing max_prepared_transactions costs ~600 bytes of shared
memory

# per transaction slot, plus lock space (see max_locks_per_transaction).

work_mem = 20000 # min 64, size in KB

maintenance_work_mem = 20000 # min 1024, size in KB

#max_stack_depth = 2048 # min 100, size in KB

Any suggestions for improvement?