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Do I use preclear when adding new parity drive

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So delivery update new drive is due today now so looking to replace my current parity drive with it, all my drives came out of my truenas set up and were tested but this will be my first new drive for unraid so hopefully someone can help on what to do to swap parity drives

Edited by robti

Solved by ConnerVT

  • Community Expert
  • Solution

There is no need to preclear a drive before using it for Parity.  The preclear application writes zeros to the entire drive to prepare it for use as a data drive in the Unraid array.  As installing a new Parity drive requires the parity to be rebuilt which will write to every location on the drive anyway.

 

Here is the relevant section from the Unraid manual for replacing a Parity drive:

https://docs.unraid.net/unraid-os/manual/storage-management#upgrading-parity-disks

 

It's not needed, but if you want to test the drive to make sure it's trustworthy and not faulty, it is a good idea to run through preclear or smart long test or other extensive workouts.

  • Author
24 minutes ago, BRiT said:

It's not needed, but if you want to test the drive to make sure it's trustworthy and not faulty, it is a good idea to run through preclear or smart long test or other extensive workouts.

so is it quite simple what to do after installing the app ?

  • 1 year later...
On 6/10/2023 at 6:24 AM, ConnerVT said:

There is no need to preclear a drive before using it for Parity.  The preclear application writes zeros to the entire drive to prepare it for use as a data drive in the Unraid array.  As installing a new Parity drive requires the parity to be rebuilt which will write to every location on the drive anyway.

 

Here is the relevant section from the Unraid manual for replacing a Parity drive:

https://docs.unraid.net/unraid-os/manual/storage-management#upgrading-parity-disks

 

You mention that adding a new hard drive as parity, UNRAID will write to every section of the new drive?

 

I use pre-clear or clear to torture test new drives for failure withing the return period.

 

Does adding a new hard drive as a parity do the same thing?

 

Thank you!

  • Community Expert

Building or rebuilding a disk (parity or otherwise) writes to every sector of a drive.

 

"Clear" is what Unraid does when you add a new data disk to an array that already has valid parity. It does this so parity will remain valid. "Clear" writes zeros to every sector.

 

"Preclear" is what you do with a preclear utility. "Preclear" can be configured to do more than simply write to every sector, with multiple passes, etc.

  • Community Expert
2 minutes ago, trurl said:

add a new data disk

I specifically mean "add", not "replace". Add to a new slot.

 

"Preclear" also can write a "preclear signature" to a disk after clearing it, so that Unraid will recognize that it has already been cleared when you add it to a new slot in the parity array.

2 hours ago, trurl said:

Building or rebuilding a disk (parity or otherwise) writes to every sector of a drive.

 

"Clear" is what Unraid does when you add a new data disk to an array that already has valid parity. It does this so parity will remain valid. "Clear" writes zeros to every sector.

 

"Preclear" is what you do with a preclear utility. "Preclear" can be configured to do more than simply write to every sector, with multiple passes, etc.

 

If I understand correctly, when I replace an existing parity drive with a larger parity drive, then UNRAID will write to EVERY SECTOR of the new drive as part of the parity building process?  Which is similar to a "torture test" to make test every sector of the drive?

 

This seems like a good practice because if there's an issue with the new drive, then we'll know right away.  Also, we will still have the existing parity drive as a backup.

 

If building parity on the new larger drive is successful, then is it okay to clear the old parity drive and add it to the array as another data drive?

 

Thanks TRURL!

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