[quote=“Brian_Hayter, post:8, topic:158752, full:true”]
Why should I take the Mac back, there is nothing wrong with it?
A chat with an Apple expert reveals Macs and TimeMachine are not happy/ideal/optimal over a network.[/quote]
There is something wrong with the Mac since you stated the Apple expert indicated that TimeMachine backups are not happy/ideal/optimal over a network.
Look, there are plenty of problems with the My Cloud. But in THIS instance the problem does not appear to be with the My Cloud the problem appears to be with El Capitan. There is a HUGE thread on the El Capitan issue(s) with the My Cloud that was posted above. Have you read through it?
The problem is people automatically knee jerk and blame the My Cloud rather than the OS (Apple or Microsoft). The very fact that you appear to indicate the My Cloud was working with Yosemite, but is not after upgrading your Mac to El Capitan indicates the problem lies with the Apple OS NOT with the My Cloud.
Copying speed when performing a backup is dependent on MANY factors including the amount of data being backed up, the network connections (WiFi vs Ethernet), the network link speed, the hard drive (both on the Mac and on the My Cloud) speed, etc. One almost NEVER sees the advertised network speed. The intial backup of any hard drive will always take the longest as all the data versus only the changed/removed data is being backed up. Perform that initial backup over WiFi and its even slower.
If you have not already done so you may want to review the following thread that discusses copy speeds and things to look out for:
