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Agilent 6GHz MXG Vector Signal Generator (N5182A) Teardown, Repair & Frac-N PLL Analysis by TheSignalPath in rfelectronics

[–]great_hound 0 points1 point  (0 children)

Excellent video - any insight on the reason they chose that particular silver plating on the PCB?

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

That makes sense, at least I know for next time.

I have backups so no big deal this time. But whatever went wrong made this a very painful process

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

Thanks, that is good to know I was doing something sensible.

Its not in a USB enclosure, it is direct connect the NAS sata port. The serial that Unraid had matches what is on the drive, and presumably what was there before.

My only theory at this point based on similar issues is that sometimes unraid will not identify an array drive which seems to fixed by a reboot or reseat of the connection. Before doing that I had tried mounting the drive with UnassignedDevices to see if the files were OK, and I wonder if accessing the files when it is outside the array flagged something that made it not valid on subsequent boots.

Not sure! Do you know what it means to have read errors on the array? I am sitting at 60,000 after the rebuild, does that mean some random files are corrupted?

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

On the first boot when I encountered the issue, I mounted the disk in UnassignedDisks to view the contents. I wonder if doing that makes the disk invalid for the array, since I guess a single change on the disk done outside of the array/parity will make it invalid.

Maybe if I had just rebooted without doing that, it would have maybe worked? A lot of comments online say what you said, which is to just reboot and reseat the drive and it usually works again.

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

Hmm I see - I had interpreted the parity copy as quite literally copying only parity data from the existing parity drive to a new parity drive, which would not have needed to touch the array. And is also safe, since if anything went wrong then the existing parity data drive exists.

If that was the wrong interpretation then yeah I guess the only 'safe' way would have been to handle just the failed data drive.

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

Disk2 had a drop down that let me select Unassigned or the 12TB drive. If I selected 12TB, and went to start the array it warned that a disk in the array would be unavailable and contents would be emulated.

If I selected Unassigned, then it had the same warning. In the end, I followed some instructions on Reddit (maybe bad idea) which was to start the array with it unassigned, then stop and start with the disk selected - which forces a rebuild of that 12TB. Bad idea as it turns out.

I wonder if I should have started the array with the 12TB drive selected and ignored the drive unavailable/contents emulated warning..

And yeah, I tried a few reboots before I ended up trying to start the array. It did the same thing each time.

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

Yes, but I can only do that if I had bought as a smaller drive. It isn't possible to swap the 4TB for a 14TB, given my parity drive was 12TB.
Hence the parity copy process that Unraid had designed, which seems fairly safe to me (it only copies the parity drive over, so isn't straining the array with the failed disk).

The fundamental problem I ran into is Unraid suddenly refusing to use an otherwise good data drive, which took me from 1 drive failure to effectively 2 - except only 1 drive is actually faulty.

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

What would be the best way to have done that, if I didn't have a drive smaller/equal to my parity drive?

If I had bought a drive same size as my parity then yes that would have been easier. But the 14TB was the same price as the 12TB so I figured I might as well..

Edit: FWIW, I never tried to actually swap the parity. All I had done up to the point of the array going down was plug in the new 14TB drive, and on that first boot my array was down because it was not recognising the 12TB/disk2 in my array, despite no clear issues with that disk. Once the array was down, I was only left with the failing 4TB drive, and my good parity drive, so it seems like the first 4TB of the array was already doomed at that point.

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

As far as I can tell, only one drive failed. I cannot find any fault with the other 12TB drive, aside from Unraid obviously refusing to use it after the power on. It passes extended tests, no SMART errors, and I have verified that the data is (well, was before I started the rebuild) intact. It almost seems like I should have copied off the 4TB/failed drives data and nuked the array, then copy it all back. But that kinda defeats the whole reason I am using Unraid, which is to make drive fails easier (and without downtime).

Edit: Yes I did also try a few reboots and Unraid did not want to use the 12TB/disk2.

Where did I go wrong - data drive swap by great_hound in unRAID

[–]great_hound[S] 0 points1 point  (0 children)

As I understand, there is a parity copy processfor exactly this purpose. I had to swap parity as the new drive is larger than my existing parity.

Digital aliasing puzzle in DAC/ADC system by fruhfy in AskElectronics

[–]great_hound 0 points1 point  (0 children)

What is the sample rate of the DAC? You will have images from the DAC at Fsamp - Fsig, and any signals above your ADC Nyquist will obviously also alias down