Planning for DR, I have to collect information

Dear All,

We are going for Disaster Recovery project, the vendor asked for more details about how much is the daily data changes only. using sar / iostat can any one help me to collect this ?!

Note: only I need the changed data size not the daily increasing data. this is to know how much size of data will transfer to the secondary site daily.

Regards

I am not sure how iostat could help here, unless it is to calculate the actual IO that will take place on your disks. To get the daily data size, using df/du will help more.