The transaction log size in Exchange 2007 is set for 1MB unlike Exchange 2003 which is 5MB. What is the reason behind this reduction on size?
The answer is ties into Exchange 2007 one of the newest future called log shipping. Where are we going to transport exchange live logs in Exchange 2007.
The answer behind this question is couple new futures offered by Exchange 07, such as local continuous replication (LCR) and cluster continuous replication (CCR).
Log Shipping ties below table
local continuous replication
cluster continuous replication
When these futures are enables, SG transaction logs get copied from the running production SG to the copy SG. The logs on the copy SG are replayed into the database to keep it up to date. The catch is that transaction logs can't be sent to the copy SG unless the log is closed on the production SG. To allow the logs close quickly, the size of the logs redeemed into 1MB versus 5MB. Also smaller transaction logs will give less risk to lose big amount of data. Honestly speaking if you lose data, you are losing data but since the mechanic is fast and risk is minimized the lost should be less and recovery time is much faster.