Hello,
We have been using Slony-I for nearly two years now for our database
system, with the following cluster :
- 6 Postgres 8.2.4 servers, four in Asia, two in Europe
- Communication occurs over a VPN, and every server can reach the others
- Roundtrip average is 300ms for Europe and Asia servers
- Data providers are in Asia, 3 million row updates / day average
(mostly split in 4 big updates / day), and at peak time, 100 updates/s
Replication basically occurs fine, to the exception that the European
servers accumulate lag for around two, three hours (six in worst cases
observed) when data processing occurs in Asia. We tried raising
"sync_group_maxsize" in every slon.conf to 24, which diminished the
number of events replication was lagging behind, but did not diminish
the lag time (Both are observed through the _SCHEMA.sl_status view, and
made into a graph through MRTG)
By reducing processed data quantities of 30%, we could reduce the lag
time by half. We also checked the VPN status, and there is no obvious
anomaly nor QoS. The only startling point would be that bandwidth usage
is extremely low, and that reducing processed data quantities did not
make the bandwidth usage fall any lower.
It looks as though as Slony is actually limiting itself to not over-use
the network's bandwidth, but actually ends up using nearly nothing.
Given our current network environment, we could perfectly cope with
Slony using 10 times more bandwidth with no problem.
Is there a way to force Slony out of it's "don't go too hard on the
network" mode (such as a setting in slon.conf)?
Thanks in advance,
--
Stephane LAPIE
Condapter / WITH EPC / Europe
Weathernews, Inc.
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