WD Red 4TB with pending sectors

Hi everyone !

I would like your opinion on a WD Red 4TB health status, to ask or not a RMA… Here the story :

The SMART infos of this disk reports “Caution” 2 current pending sectors with 956 read error rate. The quick test with DLGDIAG failed at the beginning with status code 07 (failed read test element). The extended test passed and found bad sectors that may be repairable. Bad sectors were repaired successfully by DLGDIAG, but running again the quick test always reported status code 07.
Although DLGDIAG indicates the bad sectors were repaired, the SMART status always shows 2 current pending sectors. Why aren’t they reallocated ? Is a zeroing needed to force reallocation ?

Note that this disk is part of a RAID 1 Synology NAS (SHR format) and DLGDIAG was running under Windows 10 with the disk plugged on PC. Perhaps the Synology SHR format could explained the status code 07 on DLGDIAG quick test. If the disk needs zeroing, then the RAID 1 would have to be completely rebuilt. If possible, I would like to avoid this complete rebuild.

My apologizes for my bad english and Thanks for your advices to come.

Hi @Via.Domitia

“pending sectors” are sectors which are “subject to be repaired” by the drive itself as soon as the drive has some spare time to do internal cleanup. “Pending Sectors” are nothing serios as these sectors are still blocked by the drive from being used to store data.

The repair algorythm is part of the drive firmware and starts as soon as the drive can spend some tim eon its own.

Hi Joerg_A

This seems reassuring. And what about the raw read error rate at 956 ? Is this rely on the pending sectors ? Because the synology NAS weekly reports a security risk with some I/O errors. Thanks.

Hi @Via.Domitia

let the file system repair scan the whole system. Looks like you have problems with the active file system.

Take a look at the values for “reallocated sector count” and “offline uncorrectable”. If they increase, exchange the drive.

“reallocated sector count” and “offline uncorrectable” are the count of bad sectors that “have been” or “can not be corrected”, and are the count of sectors that have problems. “Raw read error” is a value that is prior to “Pending sector”.

“Pending sector” means:
If reading a sector fails, it becomes pending. The next time you try to write to that sector, the drive attempts to rewrite it, and if that works, everything goes back to normal. If it can not correctly write the sector, then it will reallocate the sector from the spare pool. If it can’t do that - maybe it’s used up the spare pool already -, then it just becomes offline_uncorrectable and trying to read or write to it just errors out.

Therefore: the value for uncorrectable shows the “rest time to life” for the drive.

Hi Joerg_A,

Well… Now the NAS Synology says status SMART is abnormal and that I should replace the disk as soon as possible.
The count of pending sectors is always 2, just the Raw Read Error raised to 996. No reallocated sectors, no offline uncorrectable…

As you said, the Raw Read Error seems to be the main problem. I think I would go to RMA process.

Finally, I “zero” filled the HDD with DLGDIAG to force it to write on pending sectors and now they are gone without reallocated sectors. Everything goes back to normal. Just the Raw Read Error Rate reached 1062.

I put it back in the NAS and the RAID 1 has been rebuilt with normal SMART status.

I will check regularly the Raw Read Error Rate in the weeks to come.