performance testing practices

[Erik Hatcher]

This week I'm going to be incrementally loading up to 3.7M records  
into Solr, in 50k chunks.

I'd like to capture some performance numbers after each chunk to see  
how she holds up.

What numbers are folks capturing?  What techniques are you using to  
capture numbers?  I'm not looking for anything elaborate, as the goal  
is really to see how faceting fares as more data is loaded.  We've  
got some ugly data in our initial experiment, so the faceting  
concerns me.

Thanks,
        Erik