Re: [OT] Slony Triggers pulling down performance?

Ow(dot)Mun(dot)Heng(at)wdc(dot)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...
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