[Solved] preclear questions

[rcrh]

It's been a while since I've upgraded a drive and this will be the first time since I've upgraded to version 6.x so I thought I'd ask a question first.

 

I remember the preclear process taking quite a bit of time to complete so I thought that since there is now an easy way to mount a USB drive that I would run the preclear there and have it completed before I pull the old drive.  However I'm now 23 hours into the process on my 4tb drive and I'm only 69% through the pre-read process.  Here are my question:

 

When I replace the drive will unRaid recognize that the new drive has already been precleared, or will it rerun the process (ie, am I wasting my time)?

 

I'm trying to minimize the amount of time where I'm not properly protected (while the data is being rebuild from the parity).

 

Thanks in advance.

 

[trurl]

You don't mention whether USB2 or USB3. If USB2 that might be why it's taking so long. I usually do my preclears with an eSATA enclosure and it takes about 10 hours per TB or a little less for a complete cycle.

 

You also don't mention how exactly you are preclearing. There are now 2 current versions of the preclear script, one with a faster post-read, and both versions of the script are supported by the preclear plugin, which gives you a way to start and monitor your preclears in the unRAID webUI.

 

When preclear completes successfully, unRAID will recognize the disk has already been cleared.

 

Also, it is not strictly necessary for a replacement disk to be clear. Only drives added to a new slot must be clear so parity will remain valid. A clear disk is all zeros so has no impact on parity. Most people preclear new disks anyway as a test.

[JonathanM]

Not sure what exactly you are doing, but it sounds like you may be replacing an existing drive, in which case the new drive does NOT have to be precleared, it will take the same amount of time to rebuild either way. You only save time when you are populating an additional drive slot that didn't previously have a drive assigned in a parity protected array.

 

That said, you want to be sure the drive is good before you rebuild to it, so a thorough test is in order, and preclear is a great tool for testing the drive before you use it.

[rcrh]

You don't mention whether USB2 or USB3.

USB2.  So, yup, definately the slow option.  I just didn't expect it to be this slow.

 

You also don't mention how exactly you are preclearing.

I'm still in the pre-read phase so it really doesn't matter.

And I tried using the preclear plugin but in the pop up it was asking me to type "Yes" and there was no way to do that in the popup so I'm running the same command in a telnet session.

 

[rcrh]

Not sure what exactly you are doing,

I'm upgrading a drive.  Removing an existing 2tb drive and replacing it with a new 4tb drive.

 

...the new drive does NOT have to be precleared...

Most people preclear new disks anyway as a test

That is why I thought I would run the preclear first.

 

[trurl]

...And I tried using the preclear plugin but in the pop up it was asking me to type "Yes" and there was no way to do that in the popup so I'm running the same command in a telnet session.

What version of unRAID?

[rcrh]

...And I tried using the preclear plugin but in the pop up it was asking me to type "Yes" and there was no way to do that in the popup so I'm running the same command in a telnet session.

What version of unRAID?

6.1.3

BTW, on the main screen I see the status of the pre-clear under Unassigned drives and on the Settings/Preclear page.  I just couldn't start the pre-clear from the UI.

 

 

[rcrh]

42 hours in & I'm 23% through step 2 of 10.

65 hours in & I'm 83% through step 2 of 10.

72 hours in & just started the post-read (step 10 of 10)

      It might be a xmas miracle!

90 hours in & I'm 27% through step 10 of 10.

      (it might be another 40 hours at this read rate... [sigh])

113 hours in & 64% through step 10 of 10

137 hours & all steps have completed.

      (I hope it helped).