Confused about mirrored boot devices work

[STREBLO]

I'm a bit confused about how mirrored boot devices work. Are they usable without the second boot device? So if you took out one, could you boot from the single remaining device? And if you had a failure on one of them, could you add a replacement device and it would rebuild the mirror? If you did have a failure though your server would crash and you would after reboot on the remaining device, it wouldn't just keep running correct?

 

[solarisguy]

Just my FreeNAS 9.3.1 experience:

• Are they usable without the second boot device? Yes. There are some caveats, though.
  
• So if you took out one, could you boot from the single remaining device? Yes
  
• And if you had a failure on one of them, could you add a replacement device and it would rebuild the mirror? Yes. However, you need to take out the bad one first.
  
• If you did have a failure though your server would crash and you would after reboot on the remaining device, it wouldn't just keep running correct? I have no experience, yet. However, based on previous experience with FreeNAS boot drive failures I am guessing that one needs to take the bad boot device and reboot. (Which one comes first? Depends. I would say take out the bad one first.)

 

[solarisguy]

There are operating systems where a total loss of one mirror is acceptable and no interruptions occur. If you are thinking about that for FreeNAS, is not entirely like that.

Let's continue in the other thread.

 

[NAStard]

I'm interested in this topic and would dig a link to the aforementioned other thread.
thx!
:D

 

[jgreco]

The boot devices are mirrored, and if the first device has failed and the BIOS attempts to load from the second device, then the NAS will come back up but the boot pool will be degraded. If the BIOS doesn't attempt to boot from the second device (maybe throws a "Press F1" error, etc) then of course the NAS can't come back up.

 

[STREBLO]

I'm interested in this topic and would dig a link to the aforementioned other thread.
thx!
:D

QUESTION Mirror SATA DOM's

 

[solarisguy]

QUESTION Mirror SATA DOM's

Yes, and in the thread you are pointing to I gave two good reasons for doing so.

Please, please just remember about limitations...