Saving a Parity drive from Pre-Reading Phase of Preclear


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Hi all,

I bought 4 5TB Toshiba HDDs recently and it's preclearing right now along with my 4TB parity drive. Right after I typed "Yes" and hit enter for the 4TB HDD to be precleared only then I realized that if one of my data drives fail, I will have no protection. So stupid of me I know :(

 

Question is, it's still in pre-reading phase right now so.. can I cancel it and still be able to use the parity drive?

 

What I'm doing right now is that I want to use a new Toshiba HDD for the parity.

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Hi all,

I bought 4 5TB Toshiba HDDs recently and it's preclearing right now along with my 4TB parity drive. Right after I typed "Yes" and hit enter for the 4TB HDD to be precleared only then I realized that if one of my data drives fail, I will have no protection. So stupid of me I know :(

 

Question is, it's still in pre-reading phase right now so.. can I cancel it and still be able to use the parity drive?

 

What I'm doing right now is that I want to use a new Toshiba HDD for the parity. I'm using unRaid version 6.0.1 and preclear version 1.15.

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I'm confused. Did you have valid parity and then clear the configuration so you could preclear the drive? Or are you asking if you can cancel the preclear of a brand new drive and assign it to the parity slot and build parity?

 

Perhaps it would help if you described your array configuration before the drive purchase, and the array configuration currently while preclear is running, and the desired end configuration using all intended drives.

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First, if you've started clearing your parity drive, you've already invalidated parity, so you'd have to do a new parity sync to have any fault tolerance.

 

Second, you can't use a 4TB drive as parity if you're planning to add 5TB drives to the array => the parity drive must be >= the size of the largest data drive.

 

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First, if you've started clearing your parity drive, you've already invalidated parity, so you'd have to do a new parity sync to have any fault tolerance.
As long as NONE of the drives have been written to, parity is still valid. (slim chance of that though) I don't know if the preclear script writes anything to the drive until the zeroing phase, so that drive might still be valid. The rest of the array if it's been started, not so much.
Second, you can't use a 4TB drive as parity if you're planning to add 5TB drives to the array => the parity drive must be >= the size of the largest data drive.
I think he's asking about keeping the current 4TB parity drive as parity until the preclear cycle is done, trouble is, I don't know of a way to preclear a currently assigned parity drive with Joe's script, so he must have already mucked with the array configuration, which likely invalidated parity, as you said.

 

Further input from the OP is necessary for any kind of sense to be made here, but I suspect you are right Gary, parity is already invalid for one reason or another.

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Agree with don't really know the details => I assumed since the parity drive is being pre-cleared that something had already been done to remove it from the configuration, so it's likely "nuked" already.

 

But agree we need more details to know for sure.

 

bedrone => How were you able to start a pre-clear on the parity drive?    As Jonathan noted, the pre-clear script won't let you pre-clear a drive that's currently assigned to the array, so what actions did you take to allow that?

 

Also, if you're indeed planning to add the 5TB drives to the array, and have already invalidated parity; then I'd just wait for the first 5TB to finish your testing and then add it as the parity drive.

 

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Many thanks for all the replies it is very helpful. I see.. So once the preclear is started, it's previous signed status in invalidated.. 

 

Here is what I'm doing right now. I had a 4TB HDD as a parity drive and I want to upgrade it to 5TB. I bought 4 5TB HDDs and one of them will be used as parity since 5TB will be the largest size in my system. I'm doing the preclear process of all of them at once plus 4TB parity that is already in my system. So I can use 3 5TB HDDs and a 4TB HDD as data drives and a newly precleared 5TB HDD as a parity.

 

As for how to preclear a parity drive, it is easy 1) Unassign it in the array and 2) just type the parity drive letter on the console along with the preclear command.

 

I tried to use the parity drive as a data drive without preclearing it first but it didn't work. Maybe I should just format it then that would be it? I don't know.

 

The worst case scenario would be after I precleared all of 5 HDDs and tried to rebuild the parity and while doing that, one of the data drive fails and that would be the end of my precious contents on that drive because I've already zero'd out my previous parity drive. :(

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When you unassigned the parity drive, it was then a "missing" drive in your configuration.    If you had, instead, simply done a "New Config" you could have directly assigned it as a data drive.

 

What most of us would recommend, however, is that you pre-clear your NEW drives (to test them well even if they don't need clearing -- e.g. the new parity drive) BEFORE you make any configuration changes, so you maintain fault tolerance as long as possible.    But you're already past that stage, since you've already invalidated your parity drive;  so I'm simply wait for a 5TB drive to finish your pre-clearing and then assign it as parity.

 

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...I tried to use the parity drive as a data drive without preclearing it first but it didn't work. Maybe I should just format it then that would be it? I don't know...

Just preclear the old parity drive also. There are other ways but it would be more complicated to explain and would depend on exactly what you have already done.
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Ok so I stopped the 4TB parity drive just right before it's going over to the next phase of writing zeros and the stuff. Stopped it at 99% of pre-reading and..... the parity is still valid! :) I'll just put it aside for now and start building a new parity using 5TB thinking my data will be safe and insured even if bad things ever happen to my array.

Thanks again to all of you who contributed in this thread.

 

Now I have to figure out how to use "New Config" so I can use my old parity as a data drive :)

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Tools - New Config

 

But you don't actually need to do a New Config if you're simply adding a drive.  Just Stop the array and you can assign additional disks to your empty slots.    If they've been pre-cleared the process will be quick ... they'll only need formatting when you Start the array.    This includes the old parity drive AFTER you've got a new parity drive assigned and it's been rebuilt.

 

A New Config allows you to add as many drives as you want WITHOUT requiring the drives be cleared.  Since parity is going to be re-synced in this case, there's no need for clearing of any drives ... only formatting.

 

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Ok so I stopped the 4TB parity drive just right before it's going over to the next phase of writing zeros and the stuff. Stopped it at 99% of pre-reading and..... the parity is still valid! :) I'll just put it aside for now and start building a new parity using 5TB thinking my data will be safe and insured even if bad things ever happen to my array.

Thanks again to all of you who contributed in this thread.

 

Now I have to figure out how to use "New Config" so I can use my old parity as a data drive :)

 

Why do you think parity is valid? Did you run a parity check?

 

If you have coaxed the preclear script to preclear an active parity drive (which is not easy to do by accident), and stopped it before the end of the the preclear's preread cycle, I do not think parity would have been disturbed. But the only way to tell if parity is valid is to run a parity check. It is relatively easy to confuse unRAID into thinking parity is valid, but that doesn't mean it is.

 

Like everyone else here, I remain confused as to what you have done.

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I would assume the original parity is not valid at this time.  You can initiate a new parity build or just take a chance that a drive want fail.

 

These are the steps I use.  I have gone from a 3TB -> 4TB -> 4TB -> 6TB and am preclearing a 8TB now.

 

1 - Shut your server down and install the new drive.

2 - Reboot your server and ensure everything is working normally

3 - I will then do a 1, 2 and 2 cycle preclear or a 1, 3 and 3 cycle for either a 5 or 7 cycle test.  Which I choose is based on the technology of the drive, ie is it new or has been around a while and a lot of people have used it.  If it is going to fail I want it to fail now while I can exchange or return it.

4 - After the preclear, I do a new config and assign the new drive as the parity drive and let the parity rebuild.

5 - Assuming the rebuild is good, I run 1 preclear cycle on the old parity and then add it to the array.

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Actually IF the pre-clear was stopped in time AND if NO write activity has been done on the array since it was removed; it's likely that the old parity drive is indeed good, and could be re-installed with a New Config and the "trust parity" option if necessary.

 

Hopefully that won't be necessary, but it should be okay if both of those conditions are true.

 

The best approach would have been to not remove it in the first place until he was ready to switch to a 5TB parity drive; but that option is long gone.

 

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