[CentOS] Drive failed in 4-drive md RAID 10

Fri Sep 18 19:23:53 UTC 2020
Kenneth Porter <shiva at sewingwitch.com>

I got the email that a drive in my 4-drive RAID10 setup failed. What are my 

Drives are WD1000FYPS (Western Digital 1 TB 3.5" SATA).


# mdadm.conf written out by anaconda
AUTO +imsm +1.x -all
ARRAY /dev/md/root level=raid10 num-devices=4 

Personalities : [raid10]
md127 : active raid10 sdf1[2](F) sdg1[3] sde1[1] sdd1[0]
      1949480960 blocks super 1.2 512K chunks 2 near-copies [4/3] [UU_U]
      bitmap: 15/15 pages [60KB], 65536KB chunk

smartctl reports this for sdf:
197 Current_Pending_Sector  0x0012   200   200   000    Old_age   Always 
-       1
198 Offline_Uncorrectable   0x0010   200   200   000    Old_age   Offline 
-       6

So it's got 6 bad blocks, 1 pending for remapping.

Can I clear the error and rebuild? (It's not clear what commands would do 
that.) Or should I buy a replacement drive? I'm considering a WDS100T1R0A 
(2.5" 1TB red drive), which Amazon has for $135, plus the 3.5" adapter.

The system serves primarily as a home mail server (it fetchmails from an 
outside VPS serving as my domain's MX) and archival file server.