July 1, 20242 yr Hi, I'm looking to add a couple of used disks to my array. While trying to preclear the disk, `preread` seems to fail. Â dd process hung at 0, killing ... Pre-read: pre-read verification started 3 of 5 retries... Pre-Read: dd output: 0 bytes copied, 501.851 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.853 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.863 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.873 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.875 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.885 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.895 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 501.898 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in dd process hung at 0, killing ... Pre-read: pre-read verification started 4 of 5 retries... Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.505 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.515 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.744 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.767 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.777 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.786 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.796 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 502.805 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error dd process hung at 0, killing ... Pre-read: pre-read verification started 5 of 5 retries... Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.133 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.143 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.152 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.161 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.171 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.18 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-Read: dd output: 0 bytes copied, 503.189 s, 0.0 kB/s Pre-Read: dd output: dd: error reading '/dev/sdb': Input/output error Pre-Read: dd output: 0+0 records in Pre-Read: dd output: 0+0 records out Pre-read: pre-read verification failed! error encountered, exiting ... Â But if I run preclear skipping preread and postread, it succeeds. Â Preclear Disk Version: 1.0.30 Disk size: 6001175126016 Disk blocks: 1465130646 Blocks (512 bytes): 11721045168 Block size: 4096 Start sector: 0 Zeroing: zeroing the disk started 1 of 5 retries... Zeroing: emptying the MBR. Zeroing: progress - 25% zeroed @ 181 MB/s Zeroing: progress - 50% zeroed @ 167 MB/s Zeroing: progress - 75% zeroed @ 139 MB/s Zeroing: zeroing the disk completed! Signature: writing signature... Signature: verifying Unraid's signature on the MBR ... Signature: Unraid preclear signature is valid! Cycle: elapsed time: 10:48:23 Preclear: total elapsed time: 10:48:23 Â Does this mean that the disk is faulty ?
July 2, 20242 yr Community Expert Formatted with type 2 protection  You need to remove this from the disks:  https://forums.unraid.net/topic/93432-parity-disk-read-errors/?do=findComment&comment=864078 https://forums.unraid.net/topic/110835-help-with-a-sas-drive/ Â
July 5, 20242 yr Author Hi @JorgeB, Thanks, that seems to have worked. I am able to preclear those disks now. Â However, even after preclearing them, when I add the disk to the array, it still takes hours (15+) to then format the precleared disk. I thought the whole idea of preclearing was that once preclear is done (which itself takes 12+ hours) adding them to the array should be fast ? Or is my understanding wrong and preclearing the disk simply avoids the need for a parity rebuild ? I don't suppose I should format a precleared disk separately before adding it to the array ? Thanks
July 5, 20242 yr Community Expert 6 hours ago, sid said: when I add the disk to the array, it still takes hours (15+) to then format the precleared disk. Formatting does not happen at the point you add the disk.  If it was precleared and then nothing was done to the disk it should add virtually instantly.  If it was not still in a preclear state then Unraid would 'clear' it (which can be a lengthy process).  Are you sure this was not what was happening? Formatting takes place after adding the drive successfully (regardless of preclear) and normally only takes minutes.  6 hours ago, sid said: I don't suppose I should format a precleared disk separately before adding it to the array Definitely not.  This would destroy the 'preclear' state and force Unraid to go through the 'Clear' process when you add the drive to the array.  If you think something else was happening then provide new diagnostics - that might allow us to work out what happened.
July 5, 20242 yr Author It adds instantly to the array but then it says that the disk needs to be formatted. Â thevault-diagnostics-20240705-1801.zip
July 5, 20242 yr Community Expert You are getting continual errors in the syslog on that drive, and there is no SMART information for it suggesting it may have dropped offline. Â You should carefully check the the cabling and power to that drive.
July 5, 20242 yr Author The formatting status on the disk went away once diagnostics was generated 😕
July 5, 20242 yr Community Expert As I mentioned that dtive appears to have dropped offline so it not actually succeeding in the format. Â if you view the syslog via the icon at the top right of the GUI you shoul see continual errors being generated. Â
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