Just wondering if my 'Perceived' feeling that since implementing slony
for master/slave replication of select tables, my master database
performance is getting slower.

I'm constantly seeing a very high amount of IO wait. ~40-80 according to
vmstat 1

and according to atop. (hdb/hdc = raid1 mirror)
DSK | hdb | busy 83% | read 1052 | write 50 | avio 7 ms |
DSK | hdc | busy 81% | read 1248 | write 49 | avio 6 ms |


---------------------------(end of broadcast)---------------------------
TIP 5: don't forget to increase your free space map settings

Ow.Mun.Heng@wdc.com (Ow Mun Heng) writes:
> Just wondering if my 'Perceived' feeling that since implementing slony
> for master/slave replication of select tables, my master database
> performance is getting slower.
>
> I'm constantly seeing a very high amount of IO wait. ~40-80 according to
> vmstat 1
>
> and according to atop. (hdb/hdc = raid1 mirror)
> DSK | hdb | busy 83% | read 1052 | write 50 | avio 7 ms |
> DSK | hdc | busy 81% | read 1248 | write 49 | avio 6 ms |

The triggers generate some extra I/O, as they go off and write tuples
into sl_log_1/sl_log_2, so there's certainly a cost, there.

When you pull data from sl_log_1/sl_log_2, that will have a cost, too.

Replication does not come at zero cost...
--
(format nil "~S@~S" "cbbrowne" "linuxdatabases.info")
http://www3.sympatico.ca/cbbrowne/finances.html
"Power tends to corrupt and absolute power corrupts absolutely."
-- First Baron Acton, 1834 - 1902

On Fri, Jan 18, 2008 at 03:14:41PM +0800, Ow Mun Heng wrote:
> Just wondering if my 'Perceived' feeling that since implementing slony
> for master/slave replication of select tables, my master database
> performance is getting slower.

It imposes a performance penalty, yes.

A


---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to majordomo@postgresql.org so that your
message can get through to the mailing list cleanly