Parity Disk and replace for a new disk


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HI everybody,

I'm a beginner so I've got some (for a lot of you) stupid questions (and my english is terrible too, sorry):
- To replace a disk to mount a bigger one have I to got a parity disk?? If no... I have another question: my share include all my seven disks, so how can copy the files of only one of them??
- I would like to mount a Parity disk, but I'm not sure if I understood correcly: Must i mount a disk big or ugual than all my Raid? Now my Array device has 25TB , so for a parity disk have i to mount a 25TB Hard Disk????  

 

Tks for your help!!

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Unraid works best if you have a parity disk. It makes replacing data disks much easier and offers some protection against disk failure. If you don't have a parity disk you can add one but it can not be smaller than your largest data disk. So, if your largest data disk is 4 TB, you can add a parity disk of 4 TB or more. You don't need to try to find a 25 TB disk!

 

If you want to replace a data disk with a bigger one and have a parity disk, the new disk can not be bigger than the parity disk. So, choose your parity disk carefully.

 

If you want to replace a data disk with a bigger one but have no parity disk, you must copy all the files from the old disk to the new one manually. You can use the command line or mc (Midnight Commander, which is built in to Unraid) or a docker container, such as Krusader to access the disk instead of the share.

 

The best solution would be to add a parity disk first. Then replace your data disk.

 

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5 hours ago, Alcarimon said:

To replace a disk to mount a bigger one have I to got a parity disk??

You never need to have a parity disk. (I would say you should have one, but you never have to have one.)

 

5 hours ago, Alcarimon said:

- I would like to mount a Parity disk, but I'm not sure if I understood correcly: Must i mount a disk big or ugual than all my Raid? Now my Array device has 25TB , so for a parity disk have i to mount a 25TB Hard Disk????  

The parity disk/drive MUST be the biggest / largest drive. Just ONE drive that is bigger / larger than the rest (it can be *equal* size).

 

5 hours ago, Alcarimon said:

(and my english is terrible too, sorry):

I'm sorry for my interpretation of your English. I hope I helped.

 

6.

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Hello @Alcarimon,

 

12 hours ago, Alcarimon said:

To replace a disk to mount a bigger one have I to got a parity disk??

No, as stated by the others, you don't HAVE TO, it is easier

 

12 hours ago, Alcarimon said:

If no... I have another question: my share include all my seven disks, so how can copy the files of only one of them??

If you want to replace a drive, you can :

  • remove the old drive and the new drive to the array
  • mount the old drive with the Unassigned Devices plugin
  • copy the data disk to disk with Midnight Commander (mc in the terminal), Krusader or another file management docker
12 hours ago, Alcarimon said:

I would like to mount a Parity disk, but I'm not sure if I understood correcly: Must i mount a disk big or ugual than all my Raid? Now my Array device has 25TB , so for a parity disk have i to mount a 25TB Hard Disk????  

There is a misunderstanding here. The Parity drive(s) need to be as large or larger that the largest Data drive of the Array.

So if we imagine an array with Data drives like this 1x 1TB, 3x 2TB, 1x 8TB, 1x 12TB. The Parity drive(s) need to be 12TB or larger.

 

12 hours ago, Alcarimon said:

I'm a beginner so I've got some (for a lot of you) stupid questions (and my english is terrible too, sorry):

And don't worry, we all needed time to understand those topics, and your english is good enough to be understood. We are not all native english speakers here, I am not. ;) 

 

Do not hesitate if you need more details.

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16 hours ago, John_M said:

Unraid works best if you have a parity disk. It makes replacing data disks much easier and offers some protection against disk failure. If you don't have a parity disk you can add one but it can not be smaller than your largest data disk. So, if your largest data disk is 4 TB, you can add a parity disk of 4 TB or more. You don't need to try to find a 25 TB disk!

 

If you want to replace a data disk with a bigger one and have a parity disk, the new disk can not be bigger than the parity disk. So, choose your parity disk carefully.

 

If you want to replace a data disk with a bigger one but have no parity disk, you must copy all the files from the old disk to the new one manually. You can use the command line or mc (Midnight Commander, which is built in to Unraid) or a docker container, such as Krusader to access the disk instead of the share.

 

The best solution would be to add a parity disk first. Then replace your data disk.

 

WOW!! Tks you.. you've explained everything really clearly! I'll go to purchase an HD for my parity disk.!!

 

 

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9 hours ago, ChatNoir said:

Hello @Alcarimon,

 

No, as stated by the others, you don't HAVE TO, it is easier

 

If you want to replace a drive, you can :

  • remove the old drive and the new drive to the array
  • mount the old drive with the Unassigned Devices plugin
  • copy the data disk to disk with Midnight Commander (mc in the terminal), Krusader or another file management docker

There is a misunderstanding here. The Parity drive(s) need to be as large or larger that the largest Data drive of the Array.

So if we imagine an array with Data drives like this 1x 1TB, 3x 2TB, 1x 8TB, 1x 12TB. The Parity drive(s) need to be 12TB or larger.

 

And don't worry, we all needed time to understand those topics, and your english is good enough to be understood. We are not all native english speakers here, I am not. ;) 

 

Do not hesitate if you need more details.

Great!! Tks you too!!! It is very rare to find patient and available people into the forums... mostly into the Italians one!!

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  • 2 months later...

Hello to All Unraid users,

 

I am new here and I`m trying to understand the how Parity works.

I have Now 24 Bay in my Server. Each 10 TB Hddrives. So in the Enad i have effektive 240 TB Space.

But if I youse Parity in I loose 10 TB of Space for some Datasecurity. Is that correct? Help me to understand that.

Now I have 10 TB Parity Drive and 2x2 TB Disk Drives in the Array. I just eddet a new 10TB Drive an startet the Array.

It takes 12 hours before I can youse a my 10TB Disk.

Is there a way to quick frmat it?

 

Is it necessary to use Parity or I can just us ist like normal disk?

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Using parity is optional - but without it you have no protection for your data if a drive fails.    You have to decide if that matters to you.

 

When you add a new drive to a parity protected array UnRaid needs to write zeroes to every sector on the drive to avoid invalidating parity which is why you cannot use it immediately.   If you had no parity it would have been added immediately.

 

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Thank you for your quik reply.

How does Parity work? If we imagine - for exampel -  I have 230 TB full of data + 10 Parity, if 3 Disks fail that means 30 TB. How can one single 10 TB Parity disk contain all data out of 230 TB?

 

My solution was now. I had a 2x of 2TB HDDs an one 10TB diks for now. I had not so much data on them. I cleand all disks with Gparted (KnoppixLive CD/USB) and cleand the USB Flash drive with Unraid.

Installed new Unraid on my USB Drive. And Started the Array. To format the disks took me minutes.

 

Parity ist enebled now on additional 10TB disk. Now think I will risk and do not use parity.

How can I remove the Parity disk and use it like normal storege dirve? Should I completely erase the old configuration.?

Thanks for your support.

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1 hour ago, Anton2021 said:

Parity ist enebled now on additional 10TB disk. Now think I will risk and do not use parity.

How can I remove the Parity disk and use it like normal storege dirve? Should I completely erase the old configuration

  • Stop array
  • unassigned parity disk
  • start array to commit the change.

the parity disk is now free for whatever purpose you want.

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Parity doesn't contain any of your data.

4 hours ago, Anton2021 said:

How does Parity work?

Parity is a common concept in computers and communications, and it is basically the same idea wherever it is used. Parity is just an extra bit that allows a missing bit to be calculated from all the other bits.

 

https://en.wikipedia.org/wiki/Parity_bit

 

In order to calculate the data for a missing disk, all other disks plus parity must be read for the calculation.

 

 

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