Noob questions starting out

[MediaMaan]

Hey everyone.

I'm new to unRAID, but moving over from OMV5 where I ran 1 x 10TB disk in an Odroid HC2 with 2 offline USB backup disks.

 

Have 2 x 10 TB disks now - one for the array, and one for parity.  

The one that will become parity currently has all the media from the HC2 on it.  I need to get that onto unRAID.  I can use my backup USB drives, but using an old PC as unRAID server and don't know if it has USB3 ports, so would prefer to do a SATA transfer.

 

I have precleared the new 10TB disk, and added it to the array.  Right now, a single disk array.

However it shows as unmountable.  I expect I can quickly format it, but I don't want to lose the preclear status (I used a preclear plugin from Community Applications) and have to spend another 48 hours waiting for it!!! 

 

Q1 : Can I format it right away and will it maintain the preclear status?

 

My second 10TB drive with all the data on it can be mounted with Unassigned Devices I assume (I just installed the plugin).  Then I can copy over the data.

The plan is once the data is copied and several files verified, that this disk is then put through a preclear before being assigned as a parity disk.  Once assigned as parity I know it will take a day or two to build.  The goal is to transfer the data without simultaneously building parity (for speed).

 

Q2 : Is this a good way to approach it, or is the option below preferable?

 

The other option I had considered was preclearing the 10TB drive with all the data on it now, and setting it as parity, but leaving it disabled for a while.  Then I would transfer my data from the 2 external backups.  What I don't like about this scenario is that it leaves me without a backup.  If an external fails during the transfer process, and my 10TB is in the process of preclearing for parity, then I lose data.

 

Q3 : What would you consider as the best way to move the data in my situation?

 

Thanks in advance for your comments!

[itimpi]

4 minutes ago, MediaMaan said:

Q1 : Can I format it right away and will it maintain the preclear status?

Yes you can format it right away.   It will NOT maintain the preclear status as a formatted disk is by definition not in a preclear state as you have written to it in creating the data structures for its file system.   I am not sure why you think you even want to maintain a preclear status as once you have formatted the drive it is ready to receive files.

 

Unraid never NEEDS precleared drives.  When you add a parity drive every sector will be overwritten with parity data anyway so no point that I can see in attempting to preclear it first.   The only real purpose of preclear is to stress test drives if you are not sure that they are good.

[MediaMaan]

Just now, itimpi said:

Yes you can format it right away.   It will NOT maintain the preclear status as a formatted disk is by definition not in a preclear state as you have written to it in creating the data structures for its file system.   

Thanks for the reply. 

I wanted to preclear the drive as it was a warranty replacement from HGST.  Wanted to give it a good test before trusting it with any data  Of course it has been recertified, by the manufacturer, but better safe than sorry!

 

I thought I had read somewhere not to format the drive afterwards as it would lose the clear status when adding parity, and would then have to clear again.

If that is the case, what happens to the data already on the drive?  About 9TB of data will be sitting on the disk post-transfer.  I wouldn't want to transfer it, add parity, have the drive cleared, and have to add the data again through my external drives...

 

Is there no issue with copying the data, then adding the parity drive?

What happens to the array disk when the parity disk is added?

 

Sorry for all the noob questions!

[itimpi]

2 minutes ago, MediaMaan said:

I thought I had read somewhere not to format the drive afterwards as it would lose the clear status when adding parity, and would then have to clear again.

If that is the case, what happens to the data already on the drive?  About 9TB of data will be sitting on the disk post-transfer.  I wouldn't want to transfer it, add parity, have the drive cleared, and have to add the data again through my external drives...

I think you have got it backwards?   The only time a drive needs to be clear is if you want to add it as a new drive to an array that is already protected by parity.  That is so that adding the drive does not invalidate parity.   if you have not yet added the parity drive then it does not need to be clear.  When you later add the parity drive it is only the contents of the parity drive that get over-written - the data drives are untouched.

 

My suspicion is that you have gotten confused with a statement that says if you preclear a drive then do not format it BEFORE adding the drive as a new drive to the array that is already parity protected.  If using the drive for a parity drive or for rebuild purposes (or if you do not have a parity drive) then its clear status is irrelevant.

 

This is covered here in the online documentation accessible via the Manual link at the bottom of the Unraid GUI.

 

[MediaMaan]

13 minutes ago, itimpi said:

My suspicion is that you have gotten confused with a statement that says if you preclear a drive then do not format it BEFORE adding the drive as a new drive to the array that is already parity protected.  If using the drive for a parity drive or for rebuild purposes (or if you do not have a parity drive) then its clear status is irrelevant.

Ah, perhaps that is indeed the source of my confusion.  I was reading the italicized line in the wiki

Quote

It is also important to note that after completing a 'Preclear' you must not carry out any operation that will write to the drive (e.g. format it) as this will destroy the 'Clear' state.

So my understanding now is that I can format the drive, create some shares, and get transferring the data.  That's great news.

Following the data transfer, I will set up the current 10TB data disk as a parity disk, and all will be okay with the newly transferred data on the array.

 

When I add further disks to the array in future, they will be cleared by unRAID prior to being made available, since it will be a parity protected array at that time.

Thanks for the clarifications 🙂

 

[itimpi]

19 minutes ago, MediaMaan said:

When I add further disks to the array in future, they will be cleared by unRAID prior to being made available, since it will be a parity protected array at that time.

Yes. 

 

If precleared (and not formatted) before adding it then Unraid will skip the Clear step and the drive will immediately be available (to be formatted ready for use).