Ideas on why a Preclear would work fine for two drives but rebuilding parity on to them fails?

[RealActorRob]

Two 4TB drives in a DS4246 did fine on preclear but then rebuilding parity on to both (parity 2) failed with 800+ and 1200+ errors.

 

27 hr preclear ran and passed.

 

# # Step 1 of 5 - Pre-read verification: [9:04:53 @ 122 MB/s] SUCCESS # # Step 2 of 5 - Zeroing the disk: [8:41:36 @ 127 MB/s] SUCCESS # # Step 3 of 5 - Writing unRAID's Preclear signature: SUCCESS # # Step 4 of 5 - Verifying unRAID's Preclear signature: SUCCESS # # Step 5 of 5 - Post-Read verification: [9:04:38 @ 122 MB/s] SUCCESS # # # # # # # # # # # # # # # ############################################################################################################################ # Cycle elapsed time: 26:51:13 | Total elapsed time: 26:51:16 # ############################################################################################################################ ############################################################################################################################ # # # S.M.A.R.T. Status (device type: default) # # # # # # ATTRIBUTE INITIAL CYCLE 1 STATUS # # Reallocated_Sector_Ct 0 0 - # # Power_On_Hours 55151 55178 Up 27 # # Temperature_Celsius 38 42 Up 4 # # Reallocated_Event_Count 0 0 - # # Current_Pending_Sector 0 0 - # # Offline_Uncorrectable 0 0 - # # UDMA_CRC_Error_Count 0 0 - # # # # # # # # # # # ############################################################################################################################ # SMART overall-health self-assessment test result: PASSED # ############################################################################################################################ --> ATTENTION: Please take a look into the SMART report above for drive health issues. --> RESULT: Preclear Finished Successfully!.

 

Retrying now on internal backplane on my T310. 

 

 

[Vr2Io]

It shouldn't disk problem. The difference of rebuild vs preclear is most disk read in same time. Loading increase a lot.

[craigr]

Run an extended (long) SMART test.  I have had drives that pass preclrear but fail SMART.  They are in a landfill.

 

craigr

[PeteAron]

OK so i have a similar problem - i have a disk that fails with crc errors in my array, but a preclear and an extended smart test are both passed with no problem.  I dont understand how this can happen - is it possible my SATA cable is failing?

[JorgeB]

33 minutes ago, kimifelipe said:

i have a disk that fails with crc errors

CRC errors are a connection problem, usually a bad SATA cable.