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.

Hello! It seems like you’ve encountered some issues with a WD Red 4TB hard drive in your Synology NAS. Here are a few thoughts and suggestions:

  1. RAID 1 and Data Redundancy:
  • RAID 1 (mirroring) should ideally provide redundancy, meaning that if one drive fails, the other should have a copy of the data. However, if a drive is experiencing issues, it’s important to address the problem promptly to maintain the integrity of your data.
  1. SMART Status:
  • The “Caution” status and the presence of pending sectors and read errors in the SMART data are signs of potential trouble. It’s good that you are monitoring the SMART data.
  1. DLGDIAG Test Results:
  • The fact that the quick test failed and reported read errors, even though the extended test passed and repaired bad sectors, is a concern. It suggests that there might be underlying issues with the drive.
  1. Pending Sectors and Reallocation:
  • The presence of “current pending sectors” in SMART data indicates that the drive has identified problematic sectors that it hasn’t been able to reallocate. The reallocation process can happen automatically in some cases, but if it’s not occurring, it could be due to various reasons.
  1. Zeroing and Rebuilding RAID:
  • Zeroing a drive (writing zeros to the entire disk) is sometimes suggested as a way to force reallocation of sectors. However, this process will likely require rebuilding the RAID, and you should be prepared for the potential data loss during this process.
  1. Considerations:
  • Before proceeding with any further actions, it’s crucial to ensure that you have a backup of your important data. If the RAID needs to be rebuilt, there is a risk of data loss, and having a backup is a precautionary measure.
  1. Contact WD Support:
  • Considering the SMART status and the issues you’ve encountered, it might be a good idea to contact WD support. They can provide specific guidance on whether an RMA is necessary and what steps should be taken to address the pending sectors.
  1. Synology Compatibility:
  • Ensure that the hard drive model is compatible with your Synology NAS. Sometimes, specific NAS-optimized drives are recommended for use in NAS systems.

In summary, while zeroing the drive might be a potential step to force reallocation, it’s crucial to weigh the potential risks, especially considering the RAID configuration. Contacting WD support for advice tailored to your specific situation would be prudent. Always prioritize data backup and redundancy in any actions you take.