2.5TB Backup Slows Over Time using Backup Exec 12.5

[deuslugh85]

I have Backup Exec running a backup to disk job every week for a Full backup of our Mac server. The disks are 1TB external hard drives connected via eSata. Both the Windows server running Backup Exec and the Mac server are connected with a trunked 2gigabit connection. The Windows server is running Windows Server 2003 with Backup Exec for Windows Servers 12.5 Rev. 2213. The data being backed up is stored on an Apple XRAID storage unit, connected to the server via 2 fiber channels. The server is running OS X 10.5 Server. A little over 2.5 TB of data is being backed up every friday night when no one is in the building. Backups start off very fast and then slow down over time. The speed moves from 2,100.00 MB/min to as slow as 500.00 MB/min.

I use an MRTG graph for the ports being used for my XServe and PC server and it shows the decline in speed over time. Any thoughts on what might be occuring this? Other backups done within the buidling are far too fast/little to show this decline in speed over time and large file transfers from one server to the other stay consistant over time.

[drakecooper]

I had what would seem to be a similar problem, running 12.0.  Same basic setup and Backup size, but the backups are being written to a large RAID5 array.  Backups would start out fine and then slow down to about 270 Mb/min.  This started all of a sudden, previous speeds were around 3500 Mb/min, then one day it stopped working.  I discovered that the write cache on the storage array that backup exec was writing to had been turned off by the controller when i swapped a HD out and it rebuilt the array.  It never turned the write cache back on when the array returned to normal state.  I manually re-enabled it and the speed immediately returned to normal. 

May not be applicable to your situation but you might look into the caching on those external drives/controller.

Best,
joe

[MitchR]

Just to ask a stupid question - what's the nature of the source backup?  Is it possible that the backups start with large files, then toward the end run into many small files?  If this is the case, you're running into the overhead to open & close each of those files - which there's no easy way around.

[teiva-boy]

You should investigate all possible disk tuning settings both in the controller, the partitions, the formatting options, etc.  

This is good practice in general.   Not to say that BE isn't at fault yet, but troubleshooting the simple stuff that you have good knowledge of before diving into an app is often at least for me, easier.