(SOLVED) [6.9.2] Help understanding preclear results

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Posted (edited)

New unRaid user here, just getting everything set up. I've just completed a preclear on a couple of older disks (sdm and sdl) and while both show passed, one (sdm) noted the following in the SMART report.


Reallocated_Sector_Ct 43 43


My understanding is that it's a sign of drive failure, but I just wanted to confirm: is it basically a death sentence for the for the drive or does it have any life left in it. My main confusion is that they still show as "Healthy" under the SMART status in the unRaid interface (another device, sdm, failed preclear and shows unhealthy so it's an obvious bin job) so I want to make sure I'm not being all doom-and-gloom.


Diagnostics attached just in case it helps.


Edited by hoppers99
Main query solved.
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Every drive has a death sentence. 


But just like Mark Twain, "the rumors of my demise are greatly exaggerated".  It's not so much the number of reallocated sectors that is worrying, but whether the drive is stable and is not adding more reallocated sectors on a regular basis.  Use it with caution, (maybe run a second preclear to see what happens) and if it doesn't grow any more bad sectors, put it to work.


I have had 10 yr old drives continue to perform flawlessly, and I have had them die sudden and violent deaths much younger.  Keep your parity valid, and also backup important data separately.  Parity is not backup.

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Yes true, all drives die, and often enough without any warning at all. Thanks for the feedback, I'm interpreting it basically as a "use but with caution" while monitoring for further degradation.


Thanks again!

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1 hour ago, hoppers99 said:

Yes true, all drives die, and often enough without any warning at all.

Keep in mind that ALL remaining drives are required to rebuild a failed drive. So... if one of your "healthy" drives decides its time is up, you are relying on a drive you know has a questionable past to recreate the failed drive. Any data on the parity array is only as safe as your weakest drive. Only you can determine how much risk is too much.

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It isn't just the reallocated sectors, though. SMART attribute 1 (Raw Read Error Rate) is non-zero, which is not a good sign with a WD disk. Unraid doesn't monitor attribute 1 by default, because Seagate disks always show a non-zero value but you ought to be monitoring it for WD and Toshiba disks, where it should show zero. The disk (sdm) hasn't had an extended SMART test run on it during at least the last 8,000 hours, if ever, so I'd run one now. There's a bug in Unraid 6.9 that doesn't prevent disks from spinning down while an extended SMART self-test is running, so either temporarily set the spindown delay to Never or stop the array until the self-test has finished (about 9 hours).


  1 Raw_Read_Error_Rate     POSR-K   200   200   051    -    71
  3 Spin_Up_Time            POS--K   253   177   021    -    900
  4 Start_Stop_Count        -O--CK   095   095   000    -    5319
  5 Reallocated_Sector_Ct   PO--CK   199   199   140    -    43
  7 Seek_Error_Rate         -OSR-K   100   253   000    -    0
  9 Power_On_Hours          -O--CK   012   012   000    -    64298


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Good info/advice, thanks guys. I am going to get some newer 10TB drives on the way tomorrow; I think given some of these drives have had 7+ years on the go it's probably time for some replacements and 3x10TB will do a parity and 2 data drives to hold it all anyway.


One questions in preparation: Is a reasonable approach to:

 * Add one drive in as new parity and let it build. Then remove the current parity.

 * Add one the two data drives in and use unBalance on each of the older ones to clear their data and then disable the older drives one-by-one


or is there a better/safer way to approach it?

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  • hoppers99 changed the title to (SOLVED) [6.9.2] Help understanding preclear results

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