Backup causing very high WP on SQL server devices and SRDF/A to suspend

Hi,

We have an MS SQL server which is backed up using EMC Networker backup server. The disks for the server are TDEV's from VMAXe.

The devices are replicated to DR VMAX using SRDF/A. Every 2-3 days we find the RDF group suspended (CACA 10).

I ran through the performance data and found that whenever the backup runs the Read I/O goes quite high and at the same time the Write Pending also peaks causing SRDF/A to drop.

The question here is that a backup only reads data, Why would read operations cause WP to go up on the devices and the system as a whole..