Re: FreeBSD Preferred RAID controllers

[Matthew Seaman]

Gabe wrote:

--- On Mon, 2/9/09, Matthew Seaman <m.sea...@infracaninophile.co.uk> wrote:

From: Matthew Seaman <m.sea...@infracaninophile.co.uk>
Subject: Re: FreeBSD Preferred RAID controllers
To: n...@att.net
Cc: freebsd-questions@freebsd.org
Date: Monday, February 9, 2009, 3:08 PM
Gabe wrote:

Now with a gstripe+gmirror setup, would it be possible

to fail a

specific drive on purpose? I mean fail a (good) drive,

pull it out,

replace it and rebuild(?) it. I know I know, but humor

me.

Yes.

        Cheers,

        Matthew

Well, to 'fail' the drive, you'ld have to
physically pull the drive
from the chassis which will involve a power cycle unless
you've got
hot-swap drives.  Of course, you should confirm that your
system will
boot with the RAID in a degraded state and that rebuilding
the RAID will
continue even if interrupted by a reboot.  gmirror(8)
passes those
tests.  You do have to type some commands to get a mirror
to rebuild
(examples are shown in the man page) unlike some hardware
RAIDs where
simply inserting an unused disk is sufficient.

-- Dr Matthew J Seaman MA, D.Phil.                   7
Priory Courtyard
                                                 Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                 Kent, CT11
9PW

Hello again all,

So I wanted to test out gmirror on software RAID so I installed a completely 
vanilla FBSD 7, as base an install as you can get, it hasn't even been on the 
network. Anyway, I did the following upon first boot to get gmirror going:

# sysctl kern.geom.debugflags=17

Then:
# gmirror label -vb round-robin gm0 /dev/ad0

Then:
# gmirror load

Then:
# echo 'geom_mirror_load="YES"' >> /boot/loader.conf

Then I edited /etc/fstab to show:
/dev/mirror/gm0s1b    none        swap    sw              0       0
/dev/mirror/gm0s1a    /           ufs     rw              1       1
/dev/mirror/gm0s1e    /tmp        ufs rw      0   0
/dev/mirror/gm0s1f    /usr        ufs rw      2   2
/dev/mirror/gm0s1d    /var        ufs     rw              2       2

I then rebooted the system, once I setup the mirror:

# gmirror insert gm0 /dev/ad1
# gmirror status

and it shows as COMPLETE. Okay, here comes the annoying part, I've got 
hot-swappable bays and I went ahead and pulled the drive. I then tried to write 
to the disk so that it realizes the disk is no longer there:

# touch file

once I do that and execute: gmirror status it shows as degraded. All fine and 
dandy. However when it comes time to pop the drive back in the drive is not 
recognized at all. I mean, the green light on the bay comes on so it definitely 
makes a connection but then thats it, atacontrol list doesn't list it and 
gmirror status still shows the same, degraded.

What gives? I wonder if this is hardware related? Bios related even? Any clues?

See atacontrol(8)

  # atacontrol list

shows what your system knows is there

  # atacontrol attach X

where X is the channel number, probes and attaches any devices on that
channel in exactly the same way it is done at system boot.

See camcontrol(8) if you've got SCSI drives.

        Cheers,

        Matthew

--
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                 Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                 Kent, CT11 9PW

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