On Sat, 1 Dec 2007, Jan Engelhardt wrote:
On Dec 1 2007 06:19, Justin Piszcz wrote:
RAID1, 0.90.03 superblocks (in order to be compatible with LILO, if
you use 1.x superblocks with LILO you can't boot)
Says who? (Don't use LILO ;-)
I like LILO :)
, and then:
/dev/sda1+sdb1 <-> /dev/md0 <-> swap
/dev/sda2+sdb2 <-> /dev/md1 <-> /boot (ext3)
/dev/sda3+sdb3 <-> /dev/md2 <-> / (xfs)
All works fine, no issues...
Quick question though, I turned off the machine, disconnected /dev/sda
from the machine, boot from /dev/sdb, no problems, shows as degraded
RAID1. Turn the machine off. Re-attach the first drive. When I boot
my first partition either re-synced by itself or it was not degraded,
was is this?
If md0 was not touched (written to) after you disconnected sda, it also
should not be in a degraded state.
So two questions:
1) If it rebuilt by itself, how come it only rebuilt /dev/md0?
So md1/md2 was NOT rebuilt?
Correct.
2) If it did not rebuild, is it because the kernel knows it does not
need to re-calculate parity etc for swap?
Kernel does not know what's inside an md usually. And it should not
try to be smart.
Ok.
I had to:
mdadm /dev/md1 -a /dev/sda2
and
mdadm /dev/md2 -a /dev/sda3
To rebuild the /boot and /, which worked fine, I am just curious
though why it works like this, I figured it would be all or nothing.
Devices are not automatically readded. Who knows, maybe you inserted a
different disk into sda which you don't want to be overwritten.
Makes sense, I just wanted to confirm that it was normal..
More info:
Not using ANY initramfs/initrd images, everything is compiled into 1
kernel image (makes things MUCH simpler and the expected device layout
etc is always the same, unlike initrd/etc).
My expected device layout is also always the same, _with_ initrd. Why?
Simply because mdadm.conf is copied to the initrd, and mdadm will
use your defined order.
That is another way as well, people seem to be divided.
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