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jbrukardt

XFS File System Manipulation Question

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Good morning

 

I am looking to use unRAID in a rather unique configuration that I have seen a few here use.

 

I have a hardware RAID controller, an Areca 1280ML, 16 4tb drives, all configured in a RAID6.     I would plan to present this array to unRAID as a single volume, utilize no parity disk (as i have hardware parity), and simply utliize unraid for its docker and NAS functions.  

 

The reason i have the RAID behind unRAID is because I need more speed than a single disk can provide.   The RAID grants me about 1500MB/S R and 900 MB/s W, which is about what i need for a CCTV application.  

 

However, I have one question before i do this.   I periodically grow my array when i run out of space (adding additional 4tb drives, and rebuilding the hardware array).   In my current setup, I can just expand the volume and filesystem to take advantage of the additional space.  

 

I know you can do this on stock XFS with the

xfs_growfs -d /myxfs1

command without problems.

 

My question is, does unRAID interfere with this in any way, or can i grow my "singular disk"  (from unRAIDs perspective) without data loss.  

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It should work, you'll just need to do a new config and reassign the larger volume since it will be considered a different disk for unRAID.

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5 minutes ago, johnnie.black said:

It should work, you'll just need to do a new config and reassign the larger volume since it will be considered a different disk for unRAID.

hmm, can you provide further details on that?   Would unRAID see the disk as "new" and want to format it?

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Not format, but it would see it as a different disk than the one previously assigned, you'd need to do a new config to clear the assignments and re-assign it.

 

This is just an educated guess, so you'd need to test that before having important data to confirm.

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There's also another thing I was forgetting, unRAID always grows the filesystem to max at every mount, again you'd need to test to confirm, but I see no reason why it wouldn't work the same, you add the disk and expand the volume in the RAID card and unRAID would expand the filesystem at array start, avoiding the new config.

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48 minutes ago, jbrukardt said:

Good morning

 

I am looking to use unRAID in a rather unique configuration that I have seen a few here use.

 

I have a hardware RAID controller, an Areca 1280ML, 16 4tb drives, all configured in a RAID6.     I would plan to present this array to unRAID as a single volume, utilize no parity disk (as i have hardware parity), and simply utliize unraid for its docker and NAS functions.  

 

The reason i have the RAID behind unRAID is because I need more speed than a single disk can provide.   The RAID grants me about 1500MB/S R and 900 MB/s W, which is about what i need for a CCTV application.  

 

However, I have one question before i do this.   I periodically grow my array when i run out of space (adding additional 4tb drives, and rebuilding the hardware array).   In my current setup, I can just expand the volume and filesystem to take advantage of the additional space.  

 

I know you can do this on stock XFS with the


xfs_growfs -d /myxfs1

command without problems.

 

My question is, does unRAID interfere with this in any way, or can i grow my "singular disk"  (from unRAIDs perspective) without data loss.  

 

You might want to look at this thread. It contains some things to do in your go file, and also instructions for pulling smart reports from the drive embedded in your RAIDset.

 

I use a 2 disk ARC-1200 with a hardware RAID0. I use it for parity. Every time I need to grow my parity, I will grab a pair of older drives and put them into the RAID set. I went from 2 2T drive (4T parity), to 2 3T drives (6T parity) to 2 4T drives (8T parity). Every time I recreate the volume, the controller assigns a new ID, which unRAID uses to recognize the drive. Looks like a different disk. I have never tried to grow a volume (my card only allows 2 drives so how can I grow?).

 

I think there is a decent chance the Areca will not rename your volume if you add a new disk, and that the volume will just suddenly appear larger. Might confuse unRAID, not sure. You might need a new config. But as part of mounting it might just grow the disk and be pretty seamless.

 

Your ability to expand the volume once you grow it is an unknown for me. But if it worked with other OSes, and @johnnie.black seems to think it should work, it probably will.

 

Do you have a backup? I think chances of data loss are low, but I would feel better with a backup in case something went unexpected. With hardware RAID, you should have one anyway.

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thats interesting that unraid might just grow it automatically.    would be worth a try.   I can easily create a second test array, and experiment. 

 

i dont have backup, and i know that a risk, as RAID is not backup.  That said, most my data is replaceable (over time) if i were to have a complete failure

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Wait, so you are willing to play with a live dataset that's not backed up in a scenario that is not officially supported? If you have an existing XFS volume with data on it, unraid will only mount it if it was partitioned in a specific way, otherwise it will want to format it.

 

You are just playing with a test set of disks until you figure out if it's going to work for you, right?

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7 minutes ago, jonathanm said:

If you have an existing XFS volume with data on it, unraid will only mount it if it was partitioned in a specific way, otherwise it will want to format it.

 

This is an important point, and one you may not be aware of, though unRAID works with XFS it won't mount an XFS partition created outside unless it uses the correct parameters, specially the correct starting sector, worse than that it will re-partition it to comply with what's expected, so it will damage an existing partition making it then also unmountable outside unRAID.

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Ill be sure to let unraid partition it.

 

Thats interesting though that they use a custom partitioning scheme.   Meaning if you wanted to move away from unraid, you couldnt use your xfs formatted drives elsewhere.  

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4 minutes ago, jbrukardt said:

you couldnt use your xfs formatted drives elsewhere.  

 

That's not a problem, only the other way around.

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On 7/18/2017 at 3:15 PM, johnnie.black said:

There's also another thing I was forgetting, unRAID always grows the filesystem to max at every mount, again you'd need to test to confirm, but I see no reason why it wouldn't work the same, you add the disk and expand the volume in the RAID card and unRAID would expand the filesystem at array start, avoiding the new config.

 

For reference, i just tested this.   unRAID did auto grow it.   Grew the array, then the volume, in the raid hardware manager.   Rebooted into unraid.   Disk ID did change, so I had to do "new config", and reassign the larger volume, which was 3tb rather than 2, (as noted i should), but it showed up right away as 3tb, didnt need formatting, or extending, and all my data was there.  

 

Im filling it beyond the prior 2tb mark now, just to make sure its actually grown.

 

Thank you all for your excellent advice, on this topic, and all the others i've posted.  Ill be sure to update every post with success or failure for those reading in the future that may have the same problem or question.   

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