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backup db duration : very urgent

Hi . I have 2 databases on different server .
They both about the same size =54 G
But free space on db A=13.6G
db B=8.5G Backing up database A takes 1 hour
Backing up database B takes 2.5 hour. Db A is used only for reporting
When db B is production db. Is that the cause for such a big difference in backup duration?
Thak you
What kind of disk, including RAID configuration, do you have in both server?
Luis Martin
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The A db (2.5 h backup) has raid array 1+0
The other one (1 h backup) identical.

Database B probably have much bigger active portion of log and you may have havy transactional activity during the full backup. That produces much bigger "relevant part of the log" that is used during the restore to have consistent image of db from the point of time backup finished. Basicaly relevant part of the log, lsn (log sequence number) at the moment backup started and at the moment backup finished are stored during the full backup and used during the restore toghether with backed-up extents. I’m not quite sure how it exactly works but I believe that mechanismus may be (part of) reason. For more details see "Inside Microsoft SQL Server 2000" by Kalen Delaney.
Thank you so much mmarovic.