Hello guru's,

 

  I'm building my Unraid now.  I have a silly question regarding the parity drive.. I know the parity is either be larger or equal to the data drive. So, as for now, my parity drive is 1 TB and my data drive is 1 TB also..  I still have one more slot to fit another drive.. I'm thinking slap a 2 TB in it.  So, my question is.....will this work at all?    Thank you kindly.

 

klnyc

 

not really

in your case you will need to use 2T as parity

and both 1T as data

Ah man ok thanks..

If i want to swap out the 1TB parity drive into 2 TB parity drive. How I do go about this?  Do I take out 1TB parity drive  and then install the new 2TB and let it rebuild?

Sorry about the newbie question.  Thanks a million!

 

 

 

not 100% sure, but I think you can do parity swap ,

search for that  in here,

as far as I understand you would take out your parity drive and replace it with new one

and than put your parity as data drive and let it copy.

but do search first.

 

however in your case I would just replaced the parity drive and rebuild.

and than add the old parity back (!!!  do pre-clear it first though !!!)

it should not take too long to rebuild 1TB

You don't need to do a parity swap, just put in the 2TB drive as parity, when you then change(re-assign) the 1TB parity drive as a data drive, it will contain the exact same data as the the original data drive.

You could probably just add the 2TB as parity and assign the original parity as data all in one shot.

But, yes preclear the new 2TB first.

You don't need to do a parity swap, just put in the 2TB drive as parity, when you then change(re-assign) the 1TB parity drive as a data drive, it will contain the exact same data as the the original data drive.

You could probably just add the 2TB as parity and assign the original parity as data all in one shot.

But, yes preclear the new 2TB first.

 

Ok, I'm like 99% sure that isn't right, at least as written.

 

What you're describing above is actually called "swap-disable," where you have a failed disk, and replace it with a disk larger than parity.  It's largely the same procedure, you're reconstructing parity onto the new bigger drive, then using that parity to reconstruct the failed drive onto the old parity.

 

But that's neither here nor there.

 

Bottom line: 

 

Either shutdown (4.7 or 5.0 without hot-swap cages) or stop the array.

 

Install new 2TB drive.

 

Power up (or start, if 5.0 with hot-swap cages).

 

Preclear your new 2TB.

 

Once cleared, stop the array.

 

Unassign your 1TB parity disk, replacing it with your new 2TB.

 

This will cause a change in the webgui, indicating a new (blue ball) parity disk, and a checkbox to start the array and rebuild the parity drive onto the new disk.

 

Do this.

 

While the parity build is ongoing, you can go ahead and preclear the 1TB drive.  Do that.

 

After parity sync completes, check parity.

 

After parity check completes, and the preclear by now has got to be done, stop the array.

 

Reassign the now cleared 1TB drive to a data slot and start the array (yes, you do want to do this).

 

You're done!

 

As an aside, this procedure is well documented here in the wiki -->http://lime-technology.com/wiki/index.php?title=UnRAID_Manual#Add_one_or_more_new_disks, and a search for "replace parity" would have turned up similar documentation.  But as they say, you don't learn until you teach! 

 

Also, you need some more drives! 

 

 

 

 

Since you only have 1 data drive, this is trivial.

 

Just install the 2TB drive;  do a "New Config", and assign your 2 1TB drives as data drives and the 2TB drive as parity;  then Start the array.    It will build parity on the 2TB drive ... and you're done 

 

(It will then format the old 1TB parity drive for use as a data drive)

 

Pretty much what I suggested, but I don't think Unraid will even build parity(if the new parity is zero'd) or format the new[old parity] 1 TB Drive when added as data.

 

@pengrus...good thing no one's life depends on you being 99% right.  j/k. Your way also works but involves many extra steps and destroying a second copy of data that was on the old parity.

 

I'll expand:

This is actually a special degenerate case of XOR parity.

 

When there are only 2 drives, 1 data and 1 parity, and the parity and the data drives are equal in size, the parity will be an exact bit for bit duplicate of the data drive, files/directories in all.

If you XOR anything with itself, the answer is 0. So if you preclear a parity drive to all 0s and then you have 2 data drives that are exactly the same, then the parity is valid for the drives. Magic(well logic)! If you then pull the parity and add it as data, a new parity will also be all 0s since anything XOR'd with 0 is itself.

 

Reminds me of an old computer architecture interview question I once got: If you have 2 and only 2 registers, one containing data A and another containing data B, How do you swap the contents of the registers?(remember you have no extra registers to hold a temp value)

 

 

 

Since you only have 1 data drive, this is trivial.

 

Just install the 2TB drive;  do a "New Config", and assign your 2 1TB drives as data drives and the 2TB drive as parity;  then Start the array.    It will build parity on the 2TB drive ... and you're done 

 

(It will then format the old 1TB parity drive for use as a data drive)