Hard drive errors and TrueNAS

[AVB]

Not sure if this is a hardware or Performance question but I picked Hardware.

I had a pile of drives that were pulled due to a size upgrade. I go through them to make sure they pass all the smart tests and then wipe them for reuse or sale. One of the old drives had a "Reallocated Sector Count" warning in Crystal Disk which got me wondering what exactly does that mean to ZFS? The drive was one of eight in a Z2 Dev which means it could totally fail without data loss. Apparently the error isn't serious enough to cause TrueNAS to degrade the disk or the Vdev or even give an alert so could it be ignored until the drive got even worse? Is there some point that TrueNAS give a warning say when 3 drives have the error or is it dependant on being discovered when the SMART date is checked?

Asking out of curiosity more than anything else since I have not seen this error on any of my Free/TrueNAS drives before.
For those that reply thanks for clueing me in.

 

[NugentS]

It depends
It means the drive encountered a bad sector and had to reallocate the sector from spares, mapping out the bad sector

On its own its not an issue, when it turns into multiple over time then its time to start worrying. In my view, more than 5, or so, or the count rises rapidly then its time to look for a replacement drive. However even after replacing the drive I would still keep the drive (marked) and run a destructive badblocks over the drive to see what happened

 

[danb35]

One of the old drives had a "Reallocated Sector Count" warning in Crystal Disk which got me wondering what exactly does that mean to ZFS?

By itself? Nothing--it only matters to ZFS as such if the disk either returns bad data when asked, or refuses to return data at all. If the bad sector is in a place that ZFS hasn't tried to read from, it won't know that anything's wrong. But if SMART monitoring were enabled on your server, it should have been giving you warnings.

 

[AVB]

SMART is enabled which is why I was surprised I didn't get a warning.

 

[danb35]

Were email notifications enabled for SMART? It uses its own email address last time I checked.

 

[AVB]

Were email notifications enabled for SMART? It uses its own email address last time I checked.

That is a good question. I'll have to check.

 

[AVB]

Were email notifications enabled for SMART? It uses its own email address last time I checked.

It seems that it was set up only to send out Critical warnings.