Centos 5 Full backup

I think you might be using the differential and log backups incorrectly. Differential backups backup everything since the last full backup; log backups backup everything since the last log backup. The big difference in your case is that the differential backups will grow throughout the day, and will therefore take longer at, say, 4:00 PM than they did at 8:00 AM.

This is a more common way to do what I think you're trying to accomplish:

• Full backup at 1:00 AM
• Differential backup every 8 hours
• Log backup every 15 minutes

If you set things up this way, you can use log shipping to restore each log backup to server B as it is created, which would probably be quicker than using the differentials to do the same thing. If you needed to do a complete restore of the database to server B, you'd restore the full backup, then the most recent differential backup (since it contains everything since the last full), then the log backups since the most recent full or differential backup.

You are describing log shipping, but you want to use 'differential' backups instead of log backups, which is the problem with your approach. With log shipping you restore the database once, then apply log backups as they are being created on the principal site, and you never ever have to redo the initial full backup restore. Just keep applying the log shipped over every few hours and you'll have your read-only copy available.