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.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.
Sectors are not reallocated ("remapped") on a read error, that is only done when a write fails. When a read fails, the pending sector count is incremented.MrPhelps wrote:Yes, URE is an Unrecoverable Read Error, which means one bit of data irremediably lost. I'm not sure how they're related to the pending sector count, which may or may not be recovered, or remapped to other sectors. I'd like to know specifically for the ReadyNAS NV+ implementation of X-RAID, does this result in a failure of the whole array, or only a stripe ? (I understand that determining which files are affected is not easy, and that's the job of the filesystem anyway).
yoh-dah wrote:snowman136 wrote:Sooo ... if I understand you, a RAID5 or x-RAID array can rebuild the array after a drive completely fails AND there are some bad spots (unrecoverabe read errors) on the reamining drives.
Not exactly. If there's an unrecoverable error on the 2nd disk, the ReadyNAS will go into 'life-support" mode and prevent any more I/O to the data volume. If for some reason the 2nd disk refuses to join in the RAID volume, it's often possible to do so manually, but this requires some expertise and is not automatic.
MrPhelps wrote:I'd like to know what exactly needs to be done to force a drive back in the array .
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