Argumentum's Note to self

Here I’ll share solutions to simple questions I had. But I’ll forget and have to research all over again hence this Note to self.


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How to make the HDD activity LED turn on for a while ?

I needed this to find …
* Device: /dev/sdu [SAT], FAILED SMART self-check. BACK UP DATA NOW!.
… where in the case the drive with problems was at in the box/case.
Got 24 drives in that box and didn’t make me a map of where is what at.

The solution was to open a shell command and run:
sudo dd if=/dev/MyDrive of=/dev/null bs=1024k count=5000
where in my case, MyDrive was sdu
That lit it up like a charismas tree ( a one light tree )

In my system I can pull a drive ( they are hotsomething ) but you should shutdown before removing/adding any drives.


Am I running ECC memory ? ( source )

To find out, from the shell you’d run sudo dmidecode -t memory | more or sudo dmidecode 3.4 | more ( the |more pipe is to read little by little but if you have a way to scroll the output text, is not needed )

Look for Total Width and Data Width.

     Total Width: 72 bits
     Data Width: 64 bits

if is different ( 72 and 64 in this case ) is ECC otherwise, if it say something like:

     Total Width: 64 bits
     Data Width: 64 bits

is not to TrueNAS, even if the WebUI say (ECC).


“Code reviews” ( video/rant, but he is right :sweat_smile: )
Feature request: add-user-notes
The path to success for block storage.


I hope my entries helps the next soul looking for answers to these questions

…just an entry to mark it solved :slight_smile:

Well, in the Storage → Disks tab, you can see serial numbers. For me, that tells me exactly what disk needs to be taken out. I also add a little sticker to each drive showing the last 4 of the serial # to make it even easier to find.

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…you are wise, or just experienced, because not all cases have pretty lights to show activity.

…and I have this question lingering my head. If the /dev/drive changes, the user may get confused after a reboot that shows different assignments. And the reports don’t show the SN#, …it’d be so much better to have at least the last N of the serial ( if privacy is a concern, I don’t mind the full SN# ), than the current /dev/this that we get to work with.

But yes, I should add labels somewhere in the case. Is a good idea.

Reboot not relevant really. One goes to the Truenas screen to see which drive is defective (not a report), then goes to the disks screen to see the serial #. Shutdown (if needed). Replace drive. Whether or not the sd assignment changes or not doesn’t matter.

I’m old, er, experienced. Labelling is a very old idea.

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Also, drives can fail in a way that prevents using it with dd.

In this case, sometimes you end up doing the activity check on all the other drives :wink:

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