Running 2 parity, and 5 data drives. Upgraded 1 from 12tb to 16tb a few days ago, everything went fine. Today I get home and plex and filesystem running strange/not playing so I restart the array, still wonky. (Also I added intel gpu as shown in previous post a few days ago, seemed to work fine and I don't think related)

Restart into maintenance mode and it says that new disc is unmountable:wrong or no filesystem. Did some research and ran the disc check on that disc, and then the fix. It said success, and upon restart everything "works" but everything that was on that disc is gone from filesystem, says 2% utilization (was aroudn 70). Parity and everything else seems to know nothing is wrong.... what the hell do I do???

I still have the old drive and backups of the usb from last week/etc. how do rollback or save my files??

I can't believe that "fix" erased all that data and the parity in about 4 minutes?

Attach Diagnostics ZIP to your NEXT post in this thread.

Some things about your description seem wrong and/or missing some details

1 hour ago, DiscoStu said:

Restart into maintenance mode and it says that new disc is unmountable:wrong or no filesystem.

Maintenance mode does not attempt to mount any drives and it will not say that. In fact, it will not say anything about the filesystem. You would have to start in Normal (not Maintenance) mode before it would display any filesystem information. You do, however, have to start in Maintenance mode in order to check filesystem.

1 hour ago, DiscoStu said:

upon restart everything "works" but everything that was on that disc is gone from filesystem, says 2% utilization

Did you do format at any point during the disk replacement?

1 hour ago, DiscoStu said:

I can't believe that "fix" erased all that data and the parity in about 4 minutes?

I'm sure that isn't what happened. For one thing, parity doesn't have any of your data so saying it was erased doesn't really make sense.

1 hour ago, DiscoStu said:

I still have the old drive

This is probably the way forward. You can probably mount the original disk as an Unassigned Device and copy its data to the formatted replacement.

But let's take a look at the diagnostics first.

8 minutes ago, trurl said:

Attach Diagnostics ZIP to your NEXT post in this thread.

Thanks, obviously a bit panicked here so probably typed quick...

Yes normal mode showed unmountable, maintenance mode for the file system check.

Never did a format, only file system check, and "fix".

I know it doesn't have my data sorry, I guess what I'm getting at is in 4 minutes hopefully it didn't actually do anything to the parity drives so maybe they can be used to save the data still.

I have mounted my old unraid drives to windows to read, copy, and save those files if needed thankfully, only a week ago too.

My current issue, getting things back to operating so I can re build all the data. (and never ever do the filesystem check/fix again) Now though since posting this I have ANOTHER drive unmountable... so hopefully my hba card or hotswap back plate got loose and this is an easy fix. About to power down and re seat cards and cable to be sure.

diagnostics-20260127-1806.zip

Edited January 27Jan 27 by DiscoStu

7 minutes ago, DiscoStu said:

only file system check, and "fix".

I know it doesn't have my data sorry, I guess what I'm getting at is in 4 minutes hopefully it didn't actually do anything to the parity drives so maybe they can be used to save the data still.

Rebuild from parity can't fix unmountable.

Parity is usually in sync with the unmountable, and with the fixed disk. So rebuild from parity will just result in what you already have.

15 minutes ago, DiscoStu said:

(and never ever do the filesystem check/fix again)

Looks like you need to check filesystem on disks 1 and 3.

Lots of this in syslog

Jan 27 17:35:28 DiscoRaid kernel: critical medium error, dev sda, sector 35008 op 0x0:(READ) flags 0x80700 phys_seg 32 prio class 2

Looks like your flash drive is failing.

But before all that...

Have you done memtest recently?

So next time if this happens, I should remove that disc so it emulates, then format it and rebuild? (assuming the drive is still good)

What do you mean exactly when you say check filesystem on those drives? Last time I did the included check things did not go well. I am going to check all the physical connections soon.

I do have recent usb backups, and another usb stick to use... should I switch over to this immediately?

Finally, no I have not. Do you mean the bios memtest (have done that probably just under a year ago), or is there an included unraid memtest I should use?

Thanks again for your help.

I have checked just about every cable and card and everything seems to be normal. Also noticed the 2 discs having issues (1 and 3), are not connected the same way, one hba card the other straight to motherboard. This makes me think unlikely a hardware issue.

These are the last 2 drives I've upgraded, disc 1 last week, and disc 3 about a month ago.

From here I am going to do a bios memtest, and power down. I could do the filesystem check on disc 3, but obviously worried this will erase everything like last time. Is it possible the usb stick is causing all of this? Or that both drives are just failing at the same time?

4 hours ago, DiscoStu said:

So next time if this happens, I should remove that disc so it emulates, then format it and rebuild? (assuming the drive is still good)

Format is NEVER part of rebuild.

Jan 27 17:35:34 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=DRIVER_OK cmd_age=0s

Jan 27 17:35:34 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 Sense Key : 0x3 [current]

Jan 27 17:35:34 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 ASC=0x11 ASCQ=0x0

Jan 27 17:35:34 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 00 0e 41 20 00 00 34 00

Jan 27 17:35:34 DiscoRaid kernel: critical medium error, dev sda, sector 934176 op 0x0:(READ) flags 0x80700 phys_seg 2 prio class 2

Jan 27 17:39:02 DiscoRaid emhttpd: spinning down /dev/sde

Jan 27 17:56:58 DiscoRaid emhttpd: spinning down /dev/sdg

Jan 27 18:06:25 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=DRIVER_OK cmd_age=0s

Jan 27 18:06:25 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 Sense Key : 0x3 [current]

Jan 27 18:06:25 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 ASC=0x11 ASCQ=0x0

Jan 27 18:06:25 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 00 0e 3a e0 00 00 0e 00

Jan 27 18:06:25 DiscoRaid kernel: critical medium error, dev sda, sector 932576 op 0x0:(READ) flags 0x80700 phys_seg 2 prio class 2

There's a problem with the flash drive, so before proceeding with the filesystem checks, recommend replacing or reformatting it first.

9 hours ago, DiscoStu said:

then format it

You must NOT ever format a drive in this scenario as you will lose the data as a new empty file system will be created and parity updated to reflect this. You simply need to let a rebuild put back the contents. When you select the format option you get a popup dialog warning you about this.

Thanks all .

Memtest returned no errors, so seems like the USB is the cause of these issues?

I don't want to start rebuilding if this issue is going to pop up again, as I could loose another drive during the rebuild.

Also I'm assuming doing 1 drive at a time is safer than both simultaneously?

Unlikely your flash drive is the cause of your other issues, but it needs to be dealt with before proceeding.

Nobody is suggesting rebuilding anything.

Once I replace the USB, what is the suggestion?

The filesystem check/fix? It seemed to not only erase disc 1, but now it is back to unmountable again so didn't fix the issue

7 minutes ago, DiscoStu said:

what is the suggestion?

Post new diagnostics.

K, will do when I get home and replace the USB.

Thanks again for all the help.

Edited January 28Jan 28 by DiscoStu

9 hours ago, trurl said:

Post new diagnostics.

Well I thought I had another new usb stick, sadly do not. Couldn't find one small enough in person tonight, so ordered a few more. Did run a windows error check on the usb stick and passed. Posting new diagnostics, one before starting array, and one after (let me know if this is not needed). Disc 1 and Disc 3 are still unmountable. Powering down now, let me know if you folks would suggest anything else while waiting for the new usb stick

discoraid-diagnostics-20260128-1852.zip discoraid-diagnostics-20260128-1850.zip

Edited January 29Jan 29 by DiscoStu

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=DRIVER_OK cmd_age=0s

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 Sense Key : 0x3 [current]

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 ASC=0x11 ASCQ=0x0

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 03 95 6f 18 00 00 08 00

Jan 28 18:51:32 DiscoRaid kernel: critical medium error, dev sda, sector 60124952 op 0x0:(READ) flags 0x0 phys_seg 8 prio class 2

There are still flash drive errors, so I recommend replacing/reformatting it first

4 hours ago, JorgeB said:

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=DRIVER_OK cmd_age=0s

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 Sense Key : 0x3 [current]

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 ASC=0x11 ASCQ=0x0

Jan 28 18:51:32 DiscoRaid kernel: sd 0:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 03 95 6f 18 00 00 08 00

Jan 28 18:51:32 DiscoRaid kernel: critical medium error, dev sda, sector 60124952 op 0x0:(READ) flags 0x0 phys_seg 8 prio class 2

There are still flash drive errors, so I recommend replacing/reformatting it first

Thanks, figured this would be the case. I found a 32gb onn flash drive locally, but I think I'll wait another day for the SanDisk ones to arrive. Never used anything by onn before

On 1/28/2026 at 9:19 AM, trurl said:

Post new diagnostics.

Have the new usb, seemed to go / work smoothly. New Diagnostics before and after starting array attached.

Still showing disc3 and disc1 unmountable. Disc3 is at least shown in the correct spot on the array before starting, while disc1 is unassigned, and when I select that correct drive I get the red "All existing data will be OVERWRITTEN...". Also maybe worth noting the historical unassigned device huh721212ale601_8cg8g8le is the old disk1, replaced recently.

I'm terrified at this point so waiting for everyone's advice before I touch anything else, but my thoughts...

Now I'm down to no parity/protection, so first step is getting disc 1 or 3 going. At this point disk1 is already lost data from earlier (can grab hopefully from the old drive later), so first step would be to put disk1 back into the array, start, let it overwrite everything, then I'll be in the same place data wise, but with at least 1 working parity.

Then do the filesystem check / repair on disc 3? This is the part I still don't understand, last time this erased all the info that was on disc1 from the array, don't want this to happen to disc 3 as well. Also have read on a few threads the unraid live memory tester can find errors memtest86 cannot, should I also give this a run?

Thanks again

discoraid-diagnostics-20260129-2007.zip discoraid-diagnostics-20260129-2010.zip

Edited January 30Jan 30 by DiscoStu

If you already formatted disk1 earlier, so it is empty, then might as well format emulated disk1 before rebuilding it.

Check filesystem does not erase anything. The worst it could do is not fix the filesystem. No way to know at this point what happened before you started this thread so we will just proceed from this point and try to get better documentation of what is happening.

37 minutes ago, trurl said:

If you already formatted disk1 earlier, so it is empty, then might as well format emulated disk1 before rebuilding it.

I've gotten up to adding disk1 back in to rebuild, but noticed it still says unmountable while doing the rebuild now. Is this normal, and will go away when finished? Or should I stop it and start again?

I suggested you just reformat it since it seemed to be empty earlier. You could have reformatted the emulated disk before rebuilding.

Since you are rebuilding already, you can format it after rebuild finishes.

Technically, you could reformat it while rebuilding. It doesn't really matter.

how would i reformat while it is moving? I see under array operation you can press yes then format, but it lists both disk1 and disk3 there. Will this format both of them?

Sorry, no you shouldn't format disk3.

Since rebuild hasn't gone very far, just stop it.

Then check filesystem on disk3 and post the results.