Slow replication in mirrormode

I've moved to new (FAST*) hardware and I was testing how long it took 
for a empty mirrormode server to catch up with the other one. (like 
after a complete failure of one of the nodes)


I'm using a database where id2entry.bdb is ~6.6Gb. and it's taking 
surprisingly long time.
After 18 hours it has gotten around 1/4 of the way.

I'm wondering if I could speed it up by loading an LDIF backup on the 
empty server before I start it.
Are there anything special I should take into account, like regarding 
entryCSN and options to slapdadd when I load the backup?

/Peter