Could you first test the snapshot without the copying process occurring at the same time. This way we are verifying that the snapshot is set correctly. Also check to see if you have 4GB of swap space assigned in the iSCSI Volume Manager. IO performance issues can be caused by improper settings from the initiator side and the how you are using it within the iSCSI Server raid array. Also Snapshot needs 10% or more of the total size of the iSCSI Volumes to efficiently work. The manual offers additional setup recommendations for the initiator; see section – “Using snapshot with Open-E iSCSI “