Temporary disable a disk, possible?

[jowi]

I've got a disk which since yesterday, shows an increase in reallocated sectors, and unraid warns me about it. This disk has almost 50.000 hours of usage on it, so this needs to be replaced.

 

I will buy a new disk, but this disk has to be precleared etc so this will take at least a couple of days before it is ready to be swapped.

Is there some way i can prevent unraid from using the problematic disk? Like disable it? 

[John_M]

While it's desirable to test a new disk before committing it to the array, there's no requirement for it and it certainly doesn't have to be cleared before being used to replace a failing disk.

 

To answer your specific question you could stop the array, unassign the problem disk and start the array. The disk will then be emulated, using parity and all your other disks. But is that the best thing to do? What is the state of the rest of your disks? Do you have single or dual parity? Your diagnostics would help answer these questions.

[jowi]

I do have another disk that unraid is warning about, it has UDMA CRC errors. I have seen that myself a long time ago, i think that was caused when a cable was not fitted perfectly after a cleanup of the servers internals...

 

I have single parity; i was running V5 until last month. I didn't even know there was such thing as a 2nd parity disk until last week...

I run a parity check every 1st of the month, always.

 

So the quickest way would be to shut down the server, replace the disk with a new one, reboot and re-assign it to the slot of the former disk, and unraid will 'notice' this and formats the disk and rebuilds it?

 

Problem disks are disk5 (CRC errors) and disk6( reallocated sectors)

 

unraid-diagnostics-20180520-1705.zip

[pwm]

8 minutes ago, jowi said:

I do have another disk that unraid is warning about, it has UDMA CRC errors

 

UDMA is normally not something to worry too much about when rebuilding. It's about getting transfer errors between drive and controller and is normally caused by a bad cable. Sometimes caused by the controller, the PSU or the disk. But the important thing with UDMA CRC errors is that the disk will read correct data from the surface - just that it regularly needs a retransmit to get the data correctly over the cable. So a drive with UDMA CRC isn't a show-stopper when it comes to rebuilding a bad disk.

 

However, you should still not ignore UDMA CRC. So if you see the counter increment you should try a new cable. And if that doesn't help try a different controller port. And if that doesn't help consider if the power cable to the drive is good - and that the PSU is able to supply stable voltages.

[John_M]

I'd investigate the cable problem on disk 5 and leave disk 6 as it is for the time being.

 

43 minutes ago, jowi said:

So the quickest way would be to shut down the server, replace the disk with a new one, reboot and re-assign it to the slot of the former disk, and unraid will 'notice' this and formats the disk and rebuilds it?

 

Yes, except for the bit about formatting. The replacement disk is rebuilt bit-by-bit, sector-by-sector using data calculated from all your other disks (including parity). At no point is it formatted - it's just an exact replica of the disk it replaced.

[jowi]

11 minutes ago, John_M said:

I'd investigate the cable problem on disk 5 and leave disk 6 as it is for the time being.

Really? I thought reallocated sectors is a sign of a failing disk? 

The last 2 days the reallocating sectors grew from 94 to 100 today.

[John_M]

8 minutes ago, jowi said:

Really? I thought reallocated sectors is a sign of a failing disk? 

The last 2 days the reallocating sectors grew from 94 to 100 today.

 

Yes, so replace it as soon as possible. There's no need to disable it though as you suggested in your first post.

[jowi]

18 minutes ago, John_M said:

 

Yes, so replace it (==DISK6!!!) as soon as possible.

 

40 minutes ago, John_M said:

I'd investigate the cable problem on disk 5 and leave disk 6 as it is for the time being.

ok, now you lost me...

 

- disk5 has UDMA CRC errors, been there since march 2016, not growing (checked old smart reports)

- disk6 has a growing reallocation sector count...

 

I think we both mean disk6 needs replacement, right?

[John_M]

Replace disk6 as soon as you reasonably can. If in the meantime it gets dropped from the array it will be emulated. If it doesn't then leave it there until you replace it.

[jowi]

I will get a new disk first thing tomorrow

 

One more question, you said it did not need formatting, the rebuild will create an exact copy. But my current disks are all ReiserFS. Isn't it better to move to XFS when replacing a disk?

 

[pwm]

12 minutes ago, jowi said:

I will get a new disk first thing tomorrow

 

One more question, you said it did not need formatting, the rebuild will create an exact copy. But my current disks are all ReiserFS. Isn't it better to move to XFS when replacing a disk?

 

 

The only way you can change file system is by moving your files somewhere else so you get an empty disk you can reformat.

 

When unRAID rebuilds, it will do a binary block-by-block rebuild so it must always restore exactly the same file system as the original disk had. unRAID will not understand anything about file system structures - it just restores binary data in the way it was stored on the original disk.

[JonathanM]

9 minutes ago, jowi said:

I will get a new disk first thing tomorrow

 

One more question, you said it did not need formatting, the rebuild will create an exact copy. But my current disks are all ReiserFS. Isn't it better to move to XFS when replacing a disk?

 

Not possible. Parity does not hold any files, so if you format the disk, it will be blank. Parity reconstructs the entire drive, format or file system errors inclusive. It can't fix corrupt files, or be used to extract individual files. Only disks as they are currently.

 

To migrate your data to XFS, you have to have an entire drive able to be formatted as XFS. You can accomplish that several ways. Add a new drive to the array, copy data off of one of your drives to another array drive, copy data off of an array drive to external media.

[jowi]

Ok, thanks guys! Will get a new 4TB drive tomorrow. I will do a preclear session (just 1 iteration) to make sure the drive is ok prior to rebuild.