Forum Discussion

Aspirant

Dec 27, 2021

Xraid-2 with OS6.x will not allow swapping of same sized drive.

Need your expert Netgear guru help please. I have a 6-drive RAID 5 setup in a Readynas Pro running upgraded OS6.x Continues to work great for a decade. The drives are as follows: WD Red Pr...

StephenB

Guru - Experienced User

Dec 28, 2021

Readynaspro wrote:

I tried replacing the 6TB drive with another spare 6TB drive, hot, but the machine would not resynch. It saw the new 6TB drive, but would not add it to the volume via resynch. It offered to make the single 6TB drive its own volume.

Was the drive blank? Or was it formatted?

Readynaspro wrote:

But even this is weird. I thought that as soon as you pull a hot drive out of the NAS, the NAS dumps it from the array, and it is recognized as a "New" drive. It is considered a new drive, and all data is scrubbed from it by the NAS, which also reformats it. At least that is the way I remember it.

Not quite. 4.2.x firmware would automatically format a drive when you hot-inserted it, and then add it into the array. That resulted in quite a few cases of data loss (often when folks new to NAS would hot-insert an NTFS drive that had their files on it). So this was changed in OS-6 - which requires you to explicitly re-format a formatted drive before it adds to the array.

I think that when you reinserted the old drive, it did remember it was part of the array.

Readynaspro wrote:

I also believed that if I pull a small drive, I have to replace it with a drive of the largest size in the array. But apparently even this is NOT true.

Well, you were always able to replace it with a drive of the same size.

There are some other scenarios where OS-6 will let you replace a drive with a bigger one (but not the biggest). In your case you could replace the 6 TB drive with 8 or 10 TB.

That is a consequence of how XRAID handles expansion.

Readynaspro wrote:

So here is what I would like to do. I want to remove the old 6TB drive as it is getting old. And replace it with another fresher 6TB drive, without crashing the array. But how? Not so simple apparently as I thought it would be.

Can I clone the old drive onto the new drive, so that the NAS thinks it is the original 6TB drive, and accepts it? Or is the NAS looking at only serial numbers? Or is there something more to it, that I have missed?

Hot-swapping with a blank 6 TB drive should work.

Cloning will also work, as long as the NAS is powered down and you do a sector-by-sector clone. Power up after you've inserted the cloned drive into the array. It shouldn't resync.

As an aside, I don't recommend the WD Red 6 TB drive (it is SMR). I doubt you are using that, but mention it just in case.

Readynaspro
Aspirant
Dec 28, 2021
Thanks for the advice.

1. I do not remember what format that new drive was in. Not sure if NTFS and blank, or still with old data and specific format from the NAS it was originally in.

Question: With OS6, what exact format of NTFS should it be in? I think the NetGear NAS internally reformats it anyway once it is inserted. It must, since there are various partitions on it. Not sure it matters, since I will sector-by-sector clone it.

2. I am using the WD 6TB Red Pros, which I think are CMR? Not the plain Red or Red plus.

3. Good advice on powering down first before cloning the drive.
I will try that after it finishes the resynch it is presently doing.

Thanks. Much appreciate the help and confirmations.
- Readynaspro
  Aspirant
  Dec 28, 2021
  Just checked the replacement 6TB drive I was trying to use, and it was formatted NTFS.
  Guessing that is why it was rejected from the array.
  
  I suspect that in OS6.x, the only reason the old drive was accepted is because it was in the Netgear format already.
  The replacement 6TB drive was in NTFS, and thus was not accepted into the array.
  
  So what should a new drive be formatted in, so that it is accepted into the array, and the RAID 5 array rebuilds that drive and synchs? Obviously not NTFS. Maybe the drive needs to be NOT formatted?
  
  I faintly remember something else now from years ago. And that is even when completely powering down, the NAS somehow remembers what drive was where, so when you boot up, it knows if a drive was pulled while unplugged. And that destroys the array. Or am I just imagining this?
  - StephenB
    Guru - Experienced User
    Dec 28, 2021
    Readynaspro wrote:
    
    So what should a new drive be formatted in, so that it is accepted into the array, and the RAID 5 array rebuilds that drive and synchs? Obviously not NTFS. Maybe the drive needs to be NOT formatted?
    
    NOT formatted. Or you can select it from the graphic in the center of the volume tab, and then format it in the NAS. Then it will be added to the array.
    
    Readynaspro wrote:
    
    I faintly remember something else now from years ago. And that is even when completely powering down, the NAS somehow remembers what drive was where, so when you boot up, it knows if a drive was pulled while unplugged. And that destroys the array. Or am I just imagining this?
    
    Removing one drive from XRAID will degrade the array, but not destroy it.
    
    But there is some metadata on each disk partition that identifies the array and has other information about the RAID (stored in the mdadm superblock).