Possible routing issue

[Jonchill]

We have 8 sites with gig connections in a figure of 8 layout so 2 of the sites have 3 potential paths to any other site and the other 6 have two potential paths to any other site.

The two sites that have 3 paths are our two data centres and we run overnight backups between these to sites.

The issue is that if the routing for the 2 sites is forced to a single path the backups work fine, but if we change the 3 paths to be equal costs paths the backups take in the region of 50% longer.

I've put done a packet capture on the server interface and the primary connection to the WAN and it shows nothing out of the ordinary.

I've looked all over the net for help but couldn't find anything that was specific to this problem.

Wh yshould the backups take 50% longer when equal cost paths are enabled?

Any help would be much appreciated.

Thanks

Jon

 

[gdvissch]

Could it be packets are arriving in incorrect order and therefore some overhead is required to put them back in correct order?

G.