How to do a parity swap?


Recommended Posts

Hi,

I'm desperately trying to do a "Parity Swap".

If you are adding a new disk or replacing a disabled disk, try Parity-Swap.

I changed the new drive (the biggest) to parity and the old parity to the missing drive.

In an other tread i read a "copy" button should appear - but not here.

What am I missing???

Running rc16c

 

Cheers

Fireball3

Link to comment

I gave up last night.

My intention was to use the "missing" drive as a cache drive and simultaneusly put the new 4TB parity drive in use.

But obviously there seems to be an issue with the "parity-swap" function.

 

Because I didn't want to waste the night waiting for answers, I started the alternative.

Since I still had the "missing" drive, I triggered a parity rebuild.

After that I will pull the "missing" drive and use it as cache drive.

I will let unRAID rebuild the "missing" on the old parity drive.

 

Q1: Do I have to preclear a drive that is used for replacing a failed one?

Q2: Do I have to preclear a drive that I intend to use as cache?

 

Nevertheless, it remains be checked if this "parity-swap" function is broken in rc16c!

I won't be able to contribute with testing after having the 4TB parity installed.

Link to comment

If you've done what I think you have, you just lost all the data on disk #2

 

If you're doing a new parity sync onto a new parity disk, it's only using the currently configured drives to compute that parity.

 

As soon as you started that process, you lost all the parity information needed to do a rebuild of your failed disk (#2).

 

The safest way to maintain an UnRAID server is to ALWAYS have a spare drive equal to the size of your current parity drive.  Then, if a drive fails, you can simply rebuild it onto that drive.    If you want to increase the size of your parity drive, do it while the array is in good shape (no failed drives).

 

I'm not sure what you did wrong in trying the swap-disable process ... but clearly it would have been a good idea to wait for a bit of help if the data on disk #2 was something you don't currently have backed up (you should, of course, always have a current backup ... but clearly many people do not do so).

 

Link to comment

@itimpi

OK.

Will try it without preclearing.

 

@garycase

In fact, I was doing some testing until now and replacing the 500GB parity with 4TB was the first step to start with the "real" server. As I explained:

Since I still had the "missing" drive, I triggered a parity rebuild.

I pulled the "missing" drive in order to force the "parity-swap".

 

As I wasn't able to do "parity-swap", I put the "missing" drive back and started the parity rebuild on the 4TB drive. Parity was good before pulling the 500GB parity.

Everything OK. Shares were accessible during the parity rebuild.

 

I thought it would be good to practice a bit prior to "going live" with the server. I don't think that I did a mistake but it's true, that there is no step by step instruction on how to do a "parity-swap".

 

you should, of course, always have a current backup ... but clearly many people do not do so

This is funny, I read this argument every time, and I wonder how that should work?

At some point one might have tens of TB of data. Might be costly to back up that amount of data.

I fully agree with you, it would be better to do so, but it's not reasonable for private use.

 

Link to comment

I fully agree with you, it would be better to do so, but it's not reasonable for private use.

 

If your data is important enough that you are willing to build a fault-tolerant server for it, I'd think it's generally important enough to be sure you back it up.

 

It's not all that expensive to maintain backups ... you don't need another server; just a set of spare disks to write the backups to -- and these can be older smaller capacity disks that you've since replaced with larger ones.    Even if you have to buy additional disks for backup, the cost is down to < $50/TB these days (or even lower).

 

In any event, I'd certainly not want to be without backups !!    I have ~ 40TB between my two UnRAID servers; and it's ALL backed up.

 

Link to comment
  • 2 weeks later...

Because if this I created a Unraid server just to be able to test the parity swap. I have no data on the drives and I made the parity drive a 1.5TB with a data a 350MB. After completing parity check shutdown unplugged data drive and placed new 2tb drive as parity and old parity in drive slot. No button appeared.

Link to comment

Hi,

I'm desperately trying to do a "Parity Swap".

If you are adding a new disk or replacing a disabled disk, try Parity-Swap.

I changed the new drive (the biggest) to parity and the old parity to the missing drive.

In an other tread i read a "copy" button should appear - but not here.

What am I missing???

Running rc16c

 

Cheers

Fireball3

Simple quesiton -- are you saying you did both at the same time?  You can only change/remove/swap ONE drive at a time with Unraid.  Change parity -- let it rebuild on the new drive.  THEN AND ONLY THEN, change another drive.  You can't change two drives at once.  {And "trading" drives counts as changing two at once.}

 

Or said another way -- if you have a drive that failed -- you must first 'rebuild' that drive before making any other changes to the unraid box.  To recover ONE drive requires ALL OTHER drives (including the parity) to be available.

 

It sounds like you created a self-inflicted "double drive" failure...  unless I misread you.

 

~Update:  Ignore me.  See later.

Link to comment

Because if this I created a Unraid server just to be able to test the parity swap. I have no data on the drives and I made the parity drive a 1.5TB with a data a 350MB. After completing parity check shutdown unplugged data drive and placed new 2tb drive as parity and old parity in drive slot. No button appeared.

You have to start the array with the data drive missing, so it is disabled, then shut down and put the larger replacement drive in the parity slot, and the old parity drive in the disabled drive's slot. You can't do a parity swap when the array was healthy on the last shutdown, as you describe doing.
Link to comment

Hi,

I'm desperately trying to do a "Parity Swap".

If you are adding a new disk or replacing a disabled disk, try Parity-Swap.

I changed the new drive (the biggest) to parity and the old parity to the missing drive.

In an other tread i read a "copy" button should appear - but not here.

What am I missing???

Running rc16c

 

Cheers

Fireball3

 

Simple quesiton -- are you saying you did both at the same time?  You can only change/remove/swap ONE drive at a time with Unraid.  Change parity -- let it rebuild on the new drive.  THEN AND ONLY THEN, change another drive.  You can't change two drives at once.  {And "trading" drives counts as changing two at once.}

 

Or said another way -- if you have a drive that failed -- you must first 'rebuild' that drive before making any other changes to the unraid box.  To recover ONE drive requires ALL OTHER drives (including the parity) to be available.

 

It sounds like you created a self-inflicted "double drive" failure...  unless I misread you.

 

 

No. There is a special procedure called parity-swap-disabled. But the data disk must be disabled, showing a red ball to initiate this procedure. It's easy to make a disk have a red ball if needed...

Link to comment
Because if this I created a Unraid server just to be able to test the parity swap. I have no data on the drives and I made the parity drive a 1.5TB with a data a 350MB. After completing parity check shutdown unplugged data drive and placed new 2tb drive as parity and old parity in drive slot. No button appeared.

 

Thank you for confirming.

 

No. There is a special procedure called parity-swap-disabled. But the data disk must be disabled, showing a red ball to initiate this procedure. It's easy to make a disk have a red ball if needed...

Agree, this procedure exists and the screenshots I provided in my prior post show that but it doesn't work. In my screenshots you can also see that the data drive is redballed.

And after doing the parity drive swap nothing happens!

 

Now that Thornwood has the same issue I think it's a bug somewhere.

Link to comment

I created the issue by removing the data drive and yes that does make it red.

 

I have contacted Tom regarding this. I have this test server for 2 more weeks prior to selling it but then I will make a new one. So for right now here is how it should work. Do parity check. All green power off. Remove test drive power on. Now should get red ball on removed drive. Stop array replace parity drive with bigger drive, replace red ball drive with parity drive. New button should appear to do parity swap. I think it should say copy or something. At this time button does not appear.

 

Did I mis something?

Link to comment

I created the issue by removing the data drive and yes that does make it red.

 

I have contacted Tom regarding this. I have this test server for 2 more weeks prior to selling it but then I will make a new one. So for right now here is how it should work. Do parity check. All green power off. Remove test drive power on. Now should get red ball on removed drive. Stop array replace parity drive with bigger drive, replace red ball drive with parity drive. New button should appear to do parity swap. I think it should say copy or something. At this time button does not appear.

 

Did I mis something?

 

I don't have a system set up at the moment to check this, but I believe you have to unassign the missing drive;  then start the array; then stop the array; and THEN do the re-assignments [new parity, old parity in place of the missing drive] ... and finally Start the array.    Try that and see if it does the rebuild okay then.

 

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.