What happens in case of URE when recovering ?

TeknoJnky wrote:

to answer the question, it really depends on how the disk handles the ure and possibly whether its a read or write error. worst case scenario, the disk freezes and causes a multiple disk failure and the loss of data, alternatively it could just hang the rebuild process causing a hard reboot to be done. At which point the rebuild process will resume, either repeating the freeze or possibly getting through the error, or an error being generated and the device going into tech support mode. best case scenario, the error is on a write and the disk automagically reallocates to a new sector and continues on with the rebuild. These will typically be seen as 're-allocated sector count' errors in the smart diagnostics and error logs.

I believe an URE is an "unrecoverable read error" On the SMART stats this will result an increase of the "Current Pending Sector" count. I'm not sure how the NAS will handle this on a resync. However, if it did block the resync, one could clone the drive to a working drive, and then resync with the clone. That would limit the errors to the unreadable sectors. However, figuring out which files were impacted by the URE would be difficult.