Replaced disk on RAID 5 and the it failed to rebuild.

@kylenap 

Certify the disk is my recommendation.(36 hours or so to do this)

Plug in the Time Machine disks. Make sure the volume mounts. If so, initialize the disk now with SoftRAID, then click on Time Machine and "Add disk" and let it rebuild.

Ok, I'll try that. Should I keep the Time Machine unmounted during the certification process, or can it remain mounted? I have Time Machine mounted again so it can backup, but haven't touched the disk I just zeroed sectors on.

@kylenap 

If you want it unmounted, that is OK, either way.

Left the Time Machine mounted and tried certifying the disk, but it failed again after about 20 mins saying that it hung. 

Actually, an update. I restarted the certification again and so far it's been going for quite a few hours. Have it complete 3 passes, so I'll see if it completes. 

On this second try, the disk successfully certified with 0 errors. Is the next step trying to add the new disk to the volume? If so, is there anything special I should do?

@kylenap 

Because of your issues, make sure your backups are up to date. then initialize that disk and use "Add disk".

That worked. Disk was rebuilt successfully and seems to be working normally now after being added to the existing volume. Thanks for the help!