Model WD20EARS-00MVWB0 and WD20EARS-00MVWB1

I have Ready NAS Duo which had 2 drives Model WD20EARS-00MVWB0

One drive failed and has just been replaced under warranty with model WD20EARS-00MVWB1
Should I expect compatibility problem with Raid mirror

Almost the same firmware on both drives

the RAID enclosure should not have problems but try checking with the enclosure manufacturer just in case

Yup, as long the first part of the model number is the same, you should not have any problems.

The model number suffix is the “Customer Configuration Code”.

See http://community.wdc.com/t5/Desktop-Portable-Drives/Product-number-help/td-p/270798

BTW, sometimes there is a subtle difference in certain model suffixes.

For example, see http://wdc.custhelp.com/app/answers/detail/search/1/a_id/5387#jumper