Write Speeds Plummet during data protection?

Hi, i recently replaced a drive, & during the data protection phase my write speeds have dropped from the usual 100-200MBps to around 200kbps! i don’t recall this being normal… [Thunderbolt 1]

however read speeds have not been effected…

What drive did you put in? (Exact model would help trying to look it up)
Given the current mess with drive makers shifting to SMR technology rather than CMR/PMR the drive used might be something to do with it SMR has abysmal performance with sustained writes, & it’s blind luck if you make it through a rebuild.

That said, I’d expect a drop in performance, after all the drives are very busy during a rebuild.

Regarding SMR drives:
We have been able to do additional testing on the SMR drives, some of these drives are using SMR technology. This includes but is not limited to the following drives:

WD Red
Seagate Barracuda
Seagate Archive

For a list of compatible (and incompatible drives), see:

Can I really use any hard drive I want in Drobo?

For additional information on the WD drives: