Hey Guys,

 

Have been searching this for a while so wanted to know what is the best way of doing this.

 

What I want to do is replace the Parity drive from one 4TB to two 8TB drives. Whats the best way to do this.

I am expanding the parity now to 2x8TB so I can then replace the 4TB data drives to 8TB when and if they start failing at a later stage and this will give me an option to add larger drives later.

 

Below is my current structure.

Parity Drive - 4TB (Reported uncorrect 1)

Disk 1 - 4TB

Disk 2 - 4TB (UDMA CRC error count 1)

Disk 3 - 4TB (Raw read error rate 125) So i suspect this is failing.

Disk 4 - 2TB

Disk 5 - 2TB

Disk 6 - 4TB

Disk 7 - 4TB

 

Also confused about the Disk 2 and 3 errors as some forums suggest that it might just be a loose cable. 

If I replace and expand the parity 1st and if the errors in Disk 2 and Disk 3 are serious. I worry I might loose that data.

 

Attached is the diagnostics report in case anyone wants to look at it.

 

Cheers

megaatlantis-diagnostics-20200922-1958.zip

Disk3 does appear to be failing, so replace that one first, you can use the parity swap procedure.

 

CRC errors are usually not a disk problem.

1 hour ago, JorgeB said:

parity swap procedure

https://wiki.unraid.net/The_parity_swap_procedure

Thanks for the recommendation @JorgeB & @trurl.

 

The wiki link gave me an idea.

What I might do is actually swap the Disk3 4TB with a new 4TB that I am getting as an advance replacement from WD for the Parity drive.

Following https://wiki.unraid.net/Replacing_a_Data_Drive

Is there a better way to just copy the data from disk 3 to the new disk 3 without having to rebuild from parity? Just so i don't strain other drives in the process.

 

 

Once that is done I will proceed with the just removing the current parity drive and adding two new 8TB ones and rebuilding the parity.

 

Do let me know if I am not going the right way

 

Cheers

21 minutes ago, Nitesh said:

Is there a better way

Not if the disk is really failing, it can't correct any read errors, best to just do a standard rebuild.

1 hour ago, JorgeB said:

Not if the disk is really failing, it can't correct any read errors, best to just do a standard rebuild.

Yep that is true. But at this moment the parity is not in the best possible state either. Hence wanted to check if I rebuild will the parity be able to take up the extra read and writes with the error it currently has. 

You can try cloning it with dd, but if there are errors rebuild from parity.

Cool thanks @JorgeB I will give dd a try and if it fails will do a rebuild

On 9/23/2020 at 9:50 PM, JorgeB said:

Not if the disk is really failing, it can't correct any read errors, best to just do a standard rebuild.

I didn't do a dd and thought to go straight for a standard rebuild as suggested.

But I received 256 errors. These errors come from the Parity drive I believe.  I have never done a rebuild before. If anyone can shed a light if these 256 errors is considered huge in number and if there is anyway to check which data was corrupted?

 

I still have the old Disk 3 from the list above which I unassigned and have not yet erased the data from.

 

I have attached the recent diagnostics

 

Any help would Be appreciated @JorgeB @trurl

megaatlantis-diagnostics-20201022-2113.zip

Looks like a disk problem, run an extended SMART test on parity.

1 minute ago, JorgeB said:

Looks like a disk problem, run an extended SMART test on parity.

Does that mean that the new disk3 that was rebuilt has some data missing? or corrupt?

2 minutes ago, JorgeB said:

Looks like a disk problem, run an extended SMART test on parity.

Ran SMART test. Errors occurred - Check SMART report (attached)

megaatlantis-smart-20201022-2359.zip

4 minutes ago, Nitesh said:

Does that mean that the new disk3 that was rebuilt has some data missing? or corrupt?

Yep, some corruption is expected, unless by luck the failed blocks did not contain any data on the rebuilt disk.

 

3 minutes ago, Nitesh said:

Ran SMART test. Errors occurred

Disk is failing and needs to be replaced.

 

1 minute ago, JorgeB said:

Yep, some corruption is expected, unless by luck the failed blocks did not contain any data on the rebuilt disk.

 

Disk is failing and needs to be replaced.

 

Yep I knew that was happening. I just wanted to check two things

 

1) Anyway to check what the corrupt data was. As I still have the old disk3 from which I am hoping to replace this from. That is if it is possible.

2) that it would be safe for me to go ahead and rebuild the parity from scratch after the newly rebuilt disk3 had errors while rebuilding.

8 minutes ago, Nitesh said:

1) Anyway to check what the corrupt data was. As I still have the old disk3 from which I am hoping to replace this from. That is if it is possible.

You can compare files between the disks, though if there are any read errors on the old disk you won't be able to compare those.

 

10 minutes ago, Nitesh said:

2) that it would be safe for me to go ahead and rebuild the parity from scratch after the newly rebuilt disk3 had errors while rebuilding.

Yes, some data on disk3 might be corrupt but parity would be valid.

Thanks for your help @JorgeB will go ahead and create a new parity. This time installing two parities so less chances of this happening again

1 hour ago, Nitesh said:

less chances of this happening again

Do you have Notifications setup to alert you immediately by email or other agent as soon as a problem is detected?

 

5 hours ago, trurl said:

Do you have Notifications setup to alert you immediately by email or other agent as soon as a problem is detected?

 

Yes I do. Why? 

20 minutes ago, Nitesh said:

Yes I do. Why? 

Just wondering why you let things get to where you had multiple disk problems.

Nope I really didn't mean it to. 

 

The parity and the disk 3 both had problems the same day. Hence I asked the question above in my original post asking if this was the case what should I do.