ZFS question

[Jeremy Chadwick]

On Sun, Mar 24, 2013 at 08:33:42AM -0700, Jeremy Chadwick wrote:
> However, commands like "zpool status"

...and seems a typo I made in vim caused the rest of my sentence to get
deleted before I sent it out.  This should have read:

> However, commands like "zpool status" work just fine, but things like
> "zpool destroy" and so on indefinitely block ("mount drain"), which to
> me makes some degree of sense.

To expand: for example, you've lost 3 disks of a 4-disk raidz2 pool,
your data is buggered and you'll need to recover from backups.

Yes, you will need to reboot for the ZFS layer to effectively "un-wedge"
itself from whatever catatonic state its in.  No argument: this is a bug
somewhere, and my guess is that it relates to the confused state of the
devices in CAM-land.  But regardless, I think if you were to lose 3 of 4
disks on a raidz2 pool you'd have much more serious things to be worried
about than "well crap I have to issue a reboot".

And yes, I did test a reboot in the scenario I described -- the system
did reboot without physically pressing the button.  But then again, for
remotely-managed systems, administrators should have the ability to
remotely power-cycle or force resets (e.g. drop to DDB via serial
console and force a reset).

People who run servers remotely yet lack this capability are
intentionally choosing to live dangerously and I do not condone such.
These folks also make me wonder how they update world without remote
console access, since to do it right you *must* drop to single-user for
the installworld phase.

I learned my lesson of "assuming" installworld would work from
multi-user long ago when it broke one time and I ended up with a system
with broken /libexec/ld-elf* binaries.  Having to go to the datacenter
30 minutes away at 3 in the morning taught me to follow instructions.

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Mountain View, CA, US                                            |
| Making life hard for others since 1977.             PGP 4BD6C0CB |