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Spaceherpe

Slow Parity Rebuild

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So i had a drive fail. Removed the old drive, popped in a new drive and the system began rebuilding the new drive without asking me to format the new drive first. The drive rebuild is going unGodly slow, between 500kbps and 4mbps.

I'm worried that if I interrupt the rebuild to format the drive on a separate computer then return the drive for the server to rebuild, it will ignore the parity and not rebuild the drive.

 

Suggestions?

Edited by Spaceherpe

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You NEVER  need to format a drive on a data rebuild.   It occurs automatically as the drive is rebuilt!   In fact, if you format the drive you will actually lose ALL of data which was previously on that drive!!!

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I'm thinking it may be a bad SATA cable. I have a replacement, but am wary of interrupting the rebuild. Also, I am running the diagnostic now. Will post shortly.

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18 minutes ago, Frank1940 said:

You NEVER  need to format a drive on a data rebuild.   It occurs automatically as the drive is rebuilt!   In fact, if you format the drive you will actually lose ALL of data which was previously on that drive!!!

News to me. Thanks for educating me! I've been running my server for a few years now, but still consider my self a complete novice. It's great when it works, and when it doesn't...all of you here on this forum help and make it great again!

 

Thank you all!!!

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UGH! Now I'm getting this on a brand new, right out of the box HD!!!

 

Unraid Disk 1 SMART health [5]: 23-12-2018 18:55

Warning [TOWER] - reallocated sector ct is 12
TOSHIBA_HDWQ140_98G9K0JHFAYG (sde)

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Was going to say there are a couple of ATA errors but nothing that would justify those speeds, apparently you got a bad disk.

 

Looks like you already formatted disk1? Or was it empty already?

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1 hour ago, johnnie.black said:

Was going to say there are a couple of ATA errors but nothing that would justify those speeds, apparently you got a bad disk.

 

Looks like you already formatted disk1? Or was it empty already?

Brand new, fresh out of the box. 

 

If I stop the parity rebuild, will it pick back up automatically after I change out the cable? How do you recommend shutting down the server to swap the cable so the parity will pick back up?

 

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3 hours ago, Frank1940 said:

You NEVER  need to format a drive on a data rebuild.   It occurs automatically as the drive is rebuilt! 

I would actually say this differently. Format creates an empty filesystem. But you are rebuilding the filesystem with its files. There is never any actual format operation done during rebuild.

2 hours ago, Spaceherpe said:

News to me

Many people seem to have a misunderstanding of "format", thinking it means something like "prepare this disk for use" whatever that vague phrase might mean. Format actually means "write an empty filesystem to this disk". That is what it has always meant in every operating system you have ever used. Unraid treats a format exactly like it does any other write operation, by updating parity. So after formatting a disk in the array, parity agrees that the disk has an empty filesystem. If you then rebuild from parity the result is an empty filesystem. This is why

3 hours ago, Frank1940 said:

You NEVER  need to format a drive on a data rebuild. 

In fact, you MUST NOT.

2 hours ago, johnnie.black said:

Looks like you already formatted disk1? Or was it empty already?

 

1 hour ago, Spaceherpe said:

If I stop the parity rebuild, will it pick back up automatically after I change out the cable? How do you recommend shutting down the server to swap the cable so the parity will pick back up?

Rebuild always starts from the beginning. Are you rebuilding an empty filesystem?

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9 minutes ago, trurl said:

I would actually say this differently. Format creates an empty filesystem. But you are rebuilding the filesystem with its files. There is never any actual format operation done during rebuild.

Many people seem to have a misunderstanding of "format", thinking it means something like "prepare this disk for use" whatever that vague phrase might mean. Format actually means "write an empty filesystem to this disk". That is what it has always meant in every operating system you have ever used. Unraid treats a format exactly like it does any other write operation, by updating parity. So after formatting a disk in the array, parity agrees that the disk has an empty filesystem. If you then rebuild from parity the result is an empty filesystem. This is why

In fact, you MUST NOT.

 

Rebuild always starts from the beginning. Are you rebuilding an empty filesystem?

The new drive is literally out of the box.

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6 minutes ago, Spaceherpe said:

My new drive failed. I had to swap out the cable, but when I restarted it, it says drive emulated

When a disk write fails, Unraid disables it. Emulating a disabled disk is what Unraid always does until the disk is rebuilt. I just hope you didn't check a box to allow it to Format.

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2 minutes ago, Spaceherpe said:

The new drive is literally out of the box.

Are you saying the original disk had no files on it, or are you just talking here about the replacement disk?

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2 minutes ago, Spaceherpe said:

I haven't done anything. It still says emulating. I don't know how to get the disk to be rebuilt?

 

 

Stop the array.

Unassign the disk.

Start the array with the disk unassigned. This will reset that disk assignment.

Stop the array again.

Assign the disk.

Start the array to begin rebuild.

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My original drive failed. I replaced it with a brand new drive, fresh out of the box. It was doing parity rebuild, but going at only 200kbps. I replaced the cable, and rebooted. Now it shows drive disabled, contents emulated.

I have turned off my parity check in scheduler, to prevent the parity being replaced without the missing files from my failed drive. 

 

I don't know why the brand new drive isn't working, nor do I know how to have it rebuild the filesystem. I'm really novice at this stuff.

 

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1 minute ago, trurl said:

 

Stop the array.

Unassign the disk.

Start the array with the disk unassigned. This will reset that disk assignment.

Stop the array again.

Assign the disk.

Start the array to begin rebuild.

Attempting now...

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1 minute ago, Spaceherpe said:

I have turned off my parity check in scheduler, to prevent the parity being replaced without the missing files from my failed drive.

If you only have single parity, it won't even attempt to check parity with a disabled disk. In fact, it can't, since all data disks must be present and valid (enabled) to check parity.

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3 minutes ago, Spaceherpe said:

Attempting now...

HOLY CRAP! that worked! I stopped the array>removed "missing" drive> started and stopped>added "missing" drive> started...rebuild in progess now at 10MBPS.

 

Thank you!

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Still unclear though. Did the original disk have any files on it or not?

3 hours ago, johnnie.black said:

Looks like you already formatted disk1? Or was it empty already?

 

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No need to put it back. johnnie seems to think your diagnostics indicated an empty disk though. I just looked at them myself and it does look like disk1 has little or no data on it.

 

While rebuilding, you should be able to look at the contents of the emulated disk. Just go to Main - Array Devices and click on the folder icon at far right on the line for the disk and it will allow you to see what is on the emulated disk. And the contents of the emulated disk is exactly what will be rebuilt on the new disk.

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Rebuild now running at 120MBPS! Thank you guys so much for all of your help! Now I know what to do in the future AND that formatting the drive is BAAAAD.

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