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Replacing 3 Old 1-TB with 2-TB drives

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It all began with my friend needing help with swapping out 3 1TB drives for 3 2TB drives.


I pre-cleared all three drives and began the process of removing each 1TB drives (one at a time) while choosing one of the new pre-cleared 2TB drives to take its place.  Waited for the rebuilding process to complete prior to starting the whole process over for the next drive and its replacement.  When I progressed through to the final drive, everything was working as planned when I receive this popup during the rebuild of the third pre-cleared 2TB drive.


Sep 19 23:37:14 preclear_disk_WD-WX61A********: Post-Read: elapsed time - 3:56:01


This was almost the same time for all three 2TB drives to pre-clear.


The problem in Fix Common Problems was


Write Cache is disabled on parity


You may experience slow read/writes to parity. Write Cache should be enabled for better results. Read this post ( https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/2/?tab=comments#comment-755621 for more information. NOTE: If this drive is connected to your server via USB, then this test and the fix may or may not work / be accurate as USB support for smartctl and hdparm is hit and miss


So I went to the URL …..  this told me to add this is Terminal replacing the last letter with the letter of your drive.


hdparm -W 1 /dev/sdm


My drives where 2 TB (sdb), 2 TB (sdd) and 2 TB (sdh)


So I typed, in the UnraidsTerminal


hdparm -W 1 /dev/sdb

This was the output after completing the command

/dev/sdb:  setting drive write-caching to 1 (on) 

write-caching =  1 (on)


So I typed the same command using the drive letter for the next drive


hdparm -W 1 /dev/sdd

This was the output after completing the command

/dev/sdb:  setting drive write-caching to 1 (on) 

write-caching =  1 (on)


So I typed the same command using the drive letter for the last drive (that was in the process of rebuilding the drive from Cache)


hdparm -W 1 /dev/sdh


AND - Walla, CRC errors….  Pausing (rebuild).   Well of course….  I should have waited for the rebuild to complete before I wrote to the drive with this command.

I then tried to clear the CRC errors, but that didn’t work.  I ended up formatting the drive, then removing/clearing the format and then started the pre-clear program once more on the drive.


I wanted to let the Unraid programmers know that if they could somehow check for allowing the command to go through while the rebuild process was happening then they could prevent this from happening when someone does a stupid thing like I did here.  I knew better, I think its just getting old and not quite as sparky as I used to be caused the issue. 


Probably nothing can  be done because your writing directly to the drive with a command directly and not going through any other process.  I would guess….


Anyway, maybe this will help someone else to recover when making the same mistake.


Thanks for reading and I love this forum!  Its a lot of help for me!

That “Squid”


Moderator - Grand Master - Community Developer

really knows what they are talking/writing about!  That’s for sure!


Super OS UNRAID!  


I have four unraid servers which I use in my home lab.  Its been an experience learning and testing different pluggins/vms.


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