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Failed Drive - Preclear new?

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I have been using UnRaid for about a year now, and I am on 4.7


I have 4x1.5Tb (data) Green Drives (unjumpered, incorrectly alligned)

I have 1x2Tb Parity Drive (WD Green)


One of my data drives was kicked out of the array the other day, so I ran a SMART check and it checked OK.


I re added the drive, and it was rebuilt using the parity. It has run for a week, but was kicked out of the array again. I have given up on this drive and I am happy to consider it dead.



I have just purchased a 2Tb Samsung HD204UI (2TB/R54/32M) replacement.



I guess that I have two options, and would like some feedback


1) Replace the drive and let UnRaid rebuild


2) Replace the drive, run a preclear for a day then add to the array and let it rebuild.


Is it worth the risk to have the new drive in the system and leave my array unprotected while the preclear runs?

Will the preclear sig do anything since the array needs to rebuild anyway?


Awaiting your feedback.

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The preclear signature is not used when re-constructing a drive, BUT if you do not go through the process of identifying un-readable sectors you will potentially be re-constructing some file to a sector that cannot be read back.


In my opinion, it is worth the time to at least go through the pre-read phase.  At least, after it any un-readable sectors should be marked for re-allocation.

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Thanks Joe.


I have taken the advise from both posts and started the Pre-Clear. I have also taken the array offline to ensure that there is less risk to the unprotected array.


I also have fired up my trust OLD Opteron (nForce4?) box, and I am running the preclear over two 1.5Tb drives that I suspect have issues. In a seperate rig, on a seperate PSU and different cables it should ensure that the Pre-Clear gives accurate results of the drives health.


Also I have installed 5.12b on the non-production Operton box, added the "Simple Features" package to the GO script and enabled email alerts... VERY impressive! I cant wait for v5 to go final and revamp my trusty 4.7 box.

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Good news and bad...


First of all, my server runs headless. So I ran the pre clear script from a Telnet session.


I was worried about the session dropping so I set my Win7 PC to not sleep, just in case.


This didn't stop my wife restarting the pc... :( Preclear results = unknown.


Needed the server back online, so just added to the array and started. It is all good now.




Kicked off a diagnosis of the old drives (2x1.5Tb) in my test 5.12b Opteron.


Here are the results from the pre clear, but I don't really know how to read them?


Some insight would be helpful



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Blargh! I hope yours is going better than mine:


Post-Read. 11% @ 7 MB/s (56:41:04)


What sort of drive controller are you using, my preclears usually run in the 80-110MB/s range.






It's a PCI RAID card. So almost as slow as is possible. I don't recall the model and I'm not at home to check.


Up until this disk purchase, I had been using my laptop and an eSATA dock to run preclear, but the last functioning usb port on the lappy is acting up and not reading the usb stick with unRAID. It's going to have to go to the shop. Cause ~25 hours is way better than 70 hours and counting...

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All of the pending sectors went away. It's odd that there were so many to begin with on both disks. I'd run at least 3 more passes to make sure that they don't return.

Actually, I saw 5 sectors pending re-allocation on one of the reports.  That is not good after a post-read.


I'd do another preclear cycle... The fact that all could be re-written to their original locations on the disk and not re-allocated points to a power issue in many cases.  Check you are not overloading a splitter, or a power supply rail.

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