unRAID without parity drive?


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Hello,

 

i set up my first private NAS today using unRAID 5.0-rc5. My setup only contains 2 drives (3 TB each) because i initially planned to use RAID 1 with another OS but switched to unRAID now because of its very easy setup and configuration.

 

I set up unRAID, selected both disks as data (for "fun") and thought it can´t work (where is my parity?) but ... it works!

 

 

My questions

 

1. Do i now have a simple storage Volume without any protection at all?

 

If yes...

1.1 Is this behavior intended or should the GUI prevent me from adding no parity?

1.2 Is this the reason why "Parity Drive" is marked as "Optional" in the FAQ?

1.3 Why is this option not described anywhere? I find it really confusing.

 

2. Because i really want parity can i just use one disk as data and the other as parity (like RAID 1)?

2.1 If yes, after reading FAQ and stuff it seems to be painless to add another data disk if i´m runnig out of memory, right?

 

3. Do i need to preclean both of my factory-new disks? The administration website doesn´t do it - maybe because the disks were new or because i didn´t set up parity?

 

 

Thank you really much in advance.

 

Maik

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1. Yes, pretty much a JBOD with the added benefit of a joined file system. If a root level folder is present on both disks, it will show as 1 unified share if you want.

1.1 Intended

1.2 Most people want disk protection, so parity is the norm, but yes, it is optional.

1.3 See 1.2

2. Yes, as long as the disk assigned to parity is as large or larger than any protected data slot.

2.1 Yes, as long as the data disk is smaller or equal to the parity disk, otherwise you have to do a parity swap to upgrade the parity disk to the largest disk.

3. Preclea_R_ is a third party optional utility that was written to allow relatively quick insertion of new disks into an already established parity protected array. As a side benefit, it fully exercises the disks to ensure there are no obvious faults on any of the disk area. Unraid uses the ENTIRE area of every other disk to reconstruct a failed disk, not just the file system area, so it's important that the entire disk is good, even the normally unused bits.

 

The stock unraid management utility makes the assumption that the disks you add are good, and monitors them from there. Until you add a parity disk and build parity, it won't even read the unused parts of the disk, so you really have no assurance they are good. After you establish parity, adding a new disk requires that the new disk be fully filled with binary 0, so the parity is maintained. Preclear was written to do the zero write, and verify that it can be read back. The stock unraid will do that, but the array is offline while that happens, which can take more than 24 hours. Also, the stock unraid always makes the assumption that the disk worked as intended, and doesn't automatically go back and verify that the write stuck. So, monthly parity checks are a good idea to ensure the health of all the disks.

 

Preclear will fully erase all data to an unrecoverable state, so only preclear drives that you wish to blank and start over. If you preclear a disk with data on it, not even a disk recovery house will have much luck getting your files back.

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yes, you have two disks, each with their own file-system, the contents viewable in user-shares as a single set of directories/files.  It is NOT a single volume, a single file cannot span disks.

 

It is not prevented... Right now you just have no parity protection.  (yes, the parity disk is "optional")

 

Yes, you can stop the array, assign the second disk as parity, then under utils-New-Config set a new disk configuration.  When you then start the array the initial parity calc will begin.

 

You cannot add more then 2 data drives with the free version of unRAID.  Once you get and put a license file on the flash drive, you can add additional data drives.

 

Until you establish initial parity protection disks will not be cleared to all zeros by the web-admin utility.  Once you do establish parity, it will write zeros to the entire new drive unless you pre-clear the data disk being added.

 

The pre-clear process also performs as a test of the disk.  About 10 to20% of all drives have problems, even when brand new.  Most people do not leave it to chance and run through 1 or more pre-clear cycles before trusting a disk in their array.

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