I just bought a new hard drive--WD20EARX--from Amazon and installed it my newly built--first time ever--unRaid server.  I added it to the array and mounted it up and copied over 1.5tb of data.

 

It seems to be working fine--no errors at all.

 

Is it really necessary to preclear this or can I take a gamble?  How often--average percentage--do new drives fail a preclear?

 

I intend on preclearing all drives in the future, especially this used one I just got today--WD20EARS.  I am just wondering if I really need to do it to the drive I already copied the data to or can I just take a gamble?

In addition to the question I have above:

 

I just picked up my WD20EARS from the post office just now.  Opened it up: looks like it is new conditon for a new drive--well taken care of.  Anyways jumpers 7-8 aren't jumpered and I assume they never were but I don't know since this is a used drive.

 

Could I just pop this in the server, add it to the array, start it up and format it and it'd probably just work fine?  Or is there anything special I need to do since it is a WD20EARS drive?  I am running 5.0 rc3.

Nothing special for EARS. Up to 20% HDD failure rate has been reported, detected by pre-clear. How important is your data? Is it easy to restore from backup?

Wow, 20% is pretty big number.  I thought hard drives were supposed to recover from errors internally.

Wow, 20% is pretty big number.  I thought hard drives were supposed to recover from errors internally.

They re-map bad (un-readable) sectors, but they return all zeros for the un-readable sector until it is next written.

 

So, if big missing chunks of files/movies are OK, then yes, they recover from errors internally.  They just do not preserve the data.

 

About 1 in 5 drives seems to be about what is being reported for deserving an immediate RMA  (failing the pre-clear burn-in process). 

Brand does not seem to matter much, as there are failures across all manufacturers/product lines.

Ok well I'm definitely going to preclear every disk from now on thanks.

Ok well I'm definitely going to preclear every disk from now on thanks.

Even pre-clearing is not an absolute guarantee...  Some disks will fail regardless a week or two after being put in service...  Fortunately, that is far far less frequent. 

 

Google "bathtub curve" for more info.

Another added benefit of pre-clearing your drives (other than giving them a work out) is that your array is available while this is occurring.

Otherwise, when you add a drive and unRaid detects that the drive had not been pre-cleared, it will clear (write all zeros) to the drive. While this is occurring, the array will NOT be started and you will have to wait before you can access your other drives.

 

So is pre-clearing necessary? NO

Is pre-clearing a good idea? It is in my mind.

 

 

So is pre-clearing necessary? NO -- Your data isn't important.  Only mine is.

Is pre-clearing a good idea? It is in my mind.

 

There, I fixed it for you

Another added benefit of pre-clearing your drives (other than giving them a work out) is that your array is available while this is occurring.

Otherwise, when you add a drive and unRaid detects that the drive had not been pre-cleared, it will clear (write all zeros) to the drive. While this is occurring, the array will NOT be started and you will have to wait before you can access your other drives.

 

I've read this -- many people saying the same thing.  But the funny thing is, I did a lot of testing on my spare 250GB, 500GB and my new 2TB hard drives, all of which had miscellaneous data on them beforehand (or brand new).. I added them to the array, started it up and clicked format.. within seconds they were formatted and available for immediate writing to the array.

 

I have never experienced anything lengthy about formatting a disk I haven't already precleared.. pretty much instantly they were available.  I am running 5.0 rc3--I don't know if this is the reason.

 

 

Another added benefit of pre-clearing your drives (other than giving them a work out) is that your array is available while this is occurring.

Otherwise, when you add a drive and unRaid detects that the drive had not been pre-cleared, it will clear (write all zeros) to the drive. While this is occurring, the array will NOT be started and you will have to wait before you can access your other drives.

 

I've read this -- many people saying the same thing.  But the funny thing is, I did a lot of testing on my spare 250GB, 500GB and my new 2TB hard drives, all of which had miscellaneous data on them beforehand (or brand new).. I added them to the array, started it up and clicked format.. within seconds they were formatted and available for immediate writing to the array.

 

I have never experienced anything lengthy about formatting a disk I haven't already precleared.. pretty much instantly they were available.  I am running 5.0 rc3--I don't know if this is the reason.

You did not yet have a parity disk assigned, or, you more accurately, had not yet initially calculated parity.  If you did, you would have had the lengthy down-time as described.  The clearing of a subsequently added disk only occurs when adding a new disk to an already established parity protected array.

 

On the other hand, you do not know if all your disk sectors are writable (and subsequently readable) until you fill your disks and perform a parity check.  (a parity check will at least let you know if they are readable.)

 

Good luck with your server.

 

Joe L.

You're right, I have no parity at the moment.  I was hoping to add that soon.  I have the WD20EARX in there with 1.5tb of data on it now.  The WD20EARS is almost done with the pre-clearing (a few more hours).  ANd I have a HD204UI sitting out of the case, waiting for a preclear.sh on it as well.

 

What should I do now?  Add the WD20EARS after preclear and transfer the contents of WD20EARX to WD20EARS?  Then run pre-clear on the WD20EARX? At some point I want to add the parity drive as well.. which can then either be the WD20EARX or the HD204UI.

What should I do now?

 

The whole point of using unraid in the first place, instead of single disks or arrays, is that you are protected against failures of drives. Right now, you are not protected, so the best thing to do would be to use the precleared disk as a parity-drive, then if the other one fails, you still have the data.

Then, after you pre-clear another drive, copy the data to that one, so you have two drives that you know that are good, and then pre-clear the one the data was on.

From that point, preclear all the rest of the drives, so you know you have known good ones.

 

Also, when I say preclear, I mean preclear with multiple passes, since drives have been known to fail after 1 or 2 preclear-passes anyway.

Why has preclearing been added by limetech if it is such a god send? Yes community based dev is great but at some point it should be seen and considered standard issue.

Why has preclearing been added by limetech if it is such a god send? Yes community based dev is great but at some point it should be seen and considered standard issue.

Actually, it was supported.

 

From the earliest days of unRAID (version 1.xx) it has recognized a pre-clear signature and skipped the clearing step if the disk was identified as having a pre-clear signature.  (I'm gong back 6+ years. SATA drives were very rare, and very expensive.  The pre-built servers Tom sold were all IDE drives and unRAID had a max of 12 drives (11 data + parity))

 

In those days Tom sold disks that had already been pre-cleared and burned in for at least 48 hours.  The largest size disks available were 500Gig.  (and I still have the initial two I purchased back then when I purchased my older server.  They were over $300 each.  )

 

So.. unRAID supported pre-cleared disks from the beginning.  Eventually, Tom stopped trying to compete wiith Newegg and the others, he stopped selling disks.

 

Adding a disk purchased elsewhere became a real issue, as the array had to be taken off-line for many hours, making my family un-happy, as we had gotten used to it being there for movies/music.

 

I asked Tom for how the pre-clear signature was recognized, and described how I was going to write a script for all the community to use.  He supported us by sharing with me the logic needed.  The rest is history.

 

I don't really care if the script is built in, or not.  I know for sure if built in, it would never have evolved to be as through. 

 

The basic issues are two.  It would be nice to have a "Clear Drive" button.  It would be nice if it did not take the array off-line to do it.

The more robust features of verification can easily be a user-add-on.  In any case, it is easier as an add-on now...

 

thats what I'm saying.

 

 

if the Device Page had an option to clear unassigned devices without affecting the array it would be great!