Parity & Cache

[thedinz]

Very new still and learning as much as i can, i am still even on an UNraid trial but at this point i am locked in.

 

That being said at the time of setup i did not have a parity drive, I am adding that today, what does that process look like? I had help setting all this up but its time to start doing on my own. After i physically put the drive in the server and boot up what are my next steps?

 

Informational: Can someone explain how parity works because i still do not get it, i have 4 drives total, 3 of them are each 4TB and 1 is 10TB so my new parity drive is a 10TB as it needs to be as large as my largest or bigger. How does this one drive cover failures on all 4? My brain cant wrap around this. When upgrading drives (lets say i am going to replace a 4TB with a 10TB) i was told i would use the parity drive to offload a 4TB drive, remove, add bigger drive and then reload from parity. How does this process work? It must be manual no? How could i otherwise garuntee the data from the drive i am removing is on the parity? Sorry for these juvenile questions.

 

Cache drive: at the time of setup i also only had a 256GB NVME drive, its still only 50% full but regardless i will adding a 1TB NVME SSD later today along with the new parity drive. I will leave the current cache drive in place, and add this as well, how do i move everything from the old drive to this drive and make it my cache drive?

 

I think that is all for now, thanks kindly for the time.

 

[trurl]

14 minutes ago, thedinz said:

When upgrading drives (lets say i am going to replace a 4TB with a 10TB) i was told i would use the parity drive to offload a 4TB drive, remove, add bigger drive and then reload from parity. How does this process work? It must be manual no? How could i otherwise garuntee the data from the drive i am removing is on the parity?

Parity does not contain any of your data. Parity (whatever system it is used in) is just an extra bit that allows a missing bit to be calculated from all the other bits. Parity plus all other disks allow the data for a missing disk to be calculated. And the calculation is very simple, like 0+1=1

 

https://wiki.unraid.net/Manual/Overview#Parity-Protected_Array

 

[trurl]

18 minutes ago, thedinz said:

parity drive, I am adding that today

Stop the array, assign the parity disk, start the array to begin parity build.

https://wiki.unraid.net/Manual/Storage_Management#Parity_Disks

[trurl]

21 minutes ago, thedinz said:

Cache drive: at the time of setup i also only had a 256GB NVME drive, its still only 50% full but regardless i will adding a 1TB NVME SSD later today along with the new parity drive. I will leave the current cache drive in place, and add this as well, how do i move everything from the old drive to this drive and make it my cache drive?

Do you mean you intend to have 2 pools, one with 256GB and one with 1TB? That is what I would recommend since these are different sized disks, then you could have the 256GB for dockers/VMs and the 1TB for caching. There would be no redundancy for either pool like this, but cached data will be moved to the parity array anyway, and you can do backups for the docker/VM stuff.

[thedinz]

6 minutes ago, trurl said:

Do you mean you intend to have 2 pools, one with 256GB and one with 1TB? That is what I would recommend since these are different sized disks, then you could have the 256GB for dockers/VMs and the 1TB for caching. There would be no redundancy for either pool like this, but cached data will be moved to the parity array anyway, and you can do backups for the docker/VM stuff.

I was thinking about just replace one for the other, but i could also keep both for sure, how would this go? How do i add the second drive as a cache and then...... how to i set what goes where?

[thedinz]

14 minutes ago, trurl said:

Parity does not contain any of your data. Parity (whatever system it is used in) is just an extra bit that allows a missing bit to be calculated from all the other bits. Parity plus all other disks allow the data for a missing disk to be calculated. And the calculation is very simple, like 0+1=1

 

https://wiki.unraid.net/Manual/Overview#Parity-Protected_Array

 

I see, so this will come up sooner rather then later though, what WOULD the process be then to unload data from an old drive to a new drive, assuming i cannot add the other one to the machine due to no more space, i do have one of those USB-sata adapters that i have used in the past but that was on windows.

[trurl]

9 minutes ago, thedinz said:

replace one for the other

 

[trurl]

13 minutes ago, thedinz said:

I see, so this will come up sooner rather then later though, what WOULD the process be then to unload data from an old drive to a new drive, assuming i cannot add the other one to the machine due to no more space, i do have one of those USB-sata adapters that i have used in the past but that was on windows.

If you need to replace a drive, you just replace it and let it rebuild to the replacement. That is the whole point of parity.

https://wiki.unraid.net/Manual/Storage_Management#Normal_replacement

 

[thedinz]

6 minutes ago, trurl said:

 

Welp, its says currently broken on my version so not sure what next lol

[trurl]

4 minutes ago, thedinz said:

Welp, its says currently broken on my version so not sure what next lol

You must have clicked on the wrong place. If you click on the title of the thread inside that "link" box, you just get the whole thread. If you click on the little arrow at upper right, you get the specific post I was pointing you to.

[thedinz]

3 minutes ago, trurl said:

You must have clicked on the wrong place. If you click on the title of the thread inside that "link" box, you just get the whole thread. If you click on the little arrow at upper right, you get the specific post I was pointing you to.

Yup that was it, i went to the main index and clicked on replace single drive part of a cached pool