Mirroring the boot drive

[rogerh]

I think the mirror status of the boot devices is only stored on the boot devices, and restoring the config file will not affect your new, single boot device.

 

[Ericloewe]

The config has no knowledge of the boot pool, apparently.

 

[Jailer]

If I save my current config (which still has a boot mirror), my concern is that after doing a fresh install onto the DOM and then restoring from my backup, that mirror boot will become part of the config again, and I'm back where I started.

Which is exactly what will happen since you will be restoring your configuration in it's current state, degraded boot pool and all.

That's why I said earlier:

Or add a usb drive back in, resilver and then do a split and remove the usb drive.

Splitting a mirrored pool

Disclaimer: I have not actually tried this but there is no reason it shouldn't work. Backup your config just in case.

 

[rogerh]

Perhaps if the OP would please do the experiment he could tell us the outcome! We would clearly be grateful as no-one seems to have seen it in practice. BTW, if you split the mirror don't you end up with a degraded pool anyway?

 

[Ericloewe]

Which is exactly what will happen since you will be restoring your configuration in it's current state, degraded boot pool and all.

I don't think that is the case. At least some time ago, the config file was 100% oblivious of the boot pool.

Some change may be/have been introduced to allow for .System datasets on boot pools, but I imagine it wouldn't affect this scenario.

 

[ChiknNutz]

I hope it is okay to post here as it seems to be in the same vein as the OP. If not, please advise.

Perhaps I misunderstood the point of the Boot Mirror, but my impression is/was that it creates a live copy of the existing boot drive and then in the event of a corrupted or damaged original boot drive, the copied boot drive would kick in. Is this the dumbed-down essence of it or am I wrong there? From the GUI, there appears to be no means of removing the second USB drive. What happens if you simply yank out the mirrored USB drive at random or it gets physically damaged?

Last night I went thru this process for the first time and I am not sure if I fully succeeded. After plugging in the second USB drive, it went thru the process and said,

"The boot volume state is ONLINE: One or more devices is currently being resilvered. The pool will continue to function, possibly in a degraded state."

It took some time to complete, but all seemed to go well (no more Critical Alert). However, I did receive an admin email a few hours later which had the following information (only the somewhat questionable info is included here). The last two lines shown below are where I have a question...do I have an action to take here? Is the drive bad or it just needs to be wiped and the process redone?

> da1 at umass-sim1 bus 1 scbus6 target 0 lun 0
> da1: <SanDisk Cruzer Fit 1.27> Removable Direct Access SCSI-6 device
> da1: Serial Number [###]
> da1: 40.000MB/s transfers
> da1: 14907MB (30529536 512 byte sectors: 255H 63S/T 1900C)
> da1: quirks=0x2<NO_6_BYTE>
> GEOM: da1: the secondary GPT table is corrupt or invalid.
> GEOM: da1: using the primary only -- recovery suggested.

 

[Ericloewe]

Is this the dumbed-down essence of it or am I wrong there?

No. It's a ZFS mirror. Both are always in use.

If one fails while the system is up, the system will carry on normally and advise you of the situation.

If one fails while the system is shut down, you might have to hack around a bit to boot, depending on your environment's specifics.

What happens if you simply yank out the mirrored USB drive at random or it gets physically damaged?

With the system running, it should just carry on.

do I have an action to take here? Is the drive bad or it just needs to be wiped and the process redone?

I'd try wiping it and re-adding it to the boot pool. If the problem returns, file a bug report.

 

[ChiknNutz]

Thank you for the reply. I have seen some commentary that if (and when) the initial USB drive fails, the mirrored one is likely to fail in rapid succession. I guess this is due to the fact that both are being accessed and used the same amount over time, which seems to be the reason they fail. If this is in fact the case, what is the point of creating the mirror if you will simply have to replace them both almost simultaneously? I assume the likelihood of them both failing at the same time is really quite small, but would it be better to make a copy and store it rather than leave it in the computer all the time?

 

[Marc Leonard]

^THIS
... is what I've been wondering for a while... I would love to know people's thoughts on it.

 

[Ericloewe]

I have seen some commentary that if (and when) the initial USB drive fails, the mirrored one is likely to fail in rapid succession.

Only if you're using crap. Otherwise, assume that the probabilities of failure are i.i.d.

but would it be better to make a copy and store it rather than leave it in the computer all the time?

Definitely backup the config file. That'll quickly get you up and running.

 

[depasseg]

^THIS
... is what I've been wondering for a while... I would love to know people's thoughts on it.

I had one of my mirrored USB drives die and I replaced it a couple days later. No problem. And now, they are on different "wear-out" timelines.

 

[ChiknNutz]

So to test this out, I yanked out the secondary USB drive and reformatted it. I then reinserted it and the resilvering process took over and all seems to be well again. We will see if I get another email saying it is corrupt. Point to note, I have never had a USB socket be so stinking tight as the ones on this new Fractal case. I almost had to get pliers to pull it out! WTH?!