I could be wrong BUT...
> 1) Does increasing the number of replication slaves increase query
> latency on the master? We're considering tiering the replication if
> it might help - replicate the master to two slaves, each of which
> replicates to ten clients.
The slaves should only be pulling from the log file, not querying the
master data directly. But yes, I guess I could cause an additional load
on the server if there are many many slaves. But with < 10,000 updates
a day (that is 8 per minute, this shouldn't be much of a load at all.
> 2) Is there a chance that the insert latency is coming from the fact
> that the table is growing so long? At a certain point, even with
> indexes, I imagine that the engine is going to have to do some linear
Well, back to answer 1. Replication is about log's, not querying the
You mentioned updates, but what about querying the data. Do you run a
lot of queries against the data on the master server? We have a
database with 50M rows in it and we have a complicated replication
strategy for the reader just so we can take 99% of the load off the
master. We have a slave'd database just to run reports from (actually
we have a load balanced cluster of them). The master received inserts
about 20 records/s
Also, what type of database are you using? INNODB? MyISAM? If you are
running MyISAM then things can get slow on updates.