Quick question,
Setup a new machine last night with two raptor 150 disks. Setup RAID1 as
I do everywhere else, 0.90.03 superblocks (in order to be compatible with
LILO, if you use 1.x superblocks with LILO you can't boot), 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?
So two questions:
1) If it rebuilt by itself, how come it only rebuilt /dev/md0?
2) If it did not rebuild, is it because the kernel knows it does not need
to re-calculate parity etc for swap?
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.
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).
Justin.
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 ;-)
, 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?
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.
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.
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.
On Sat, 1 Dec 2007, Jan Engelhardt wrote:
On Dec 1 2007 06:19, Justin Piszcz wrote:
quoted
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 :)
quoted
, 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.
quoted
So two questions:
1) If it rebuilt by itself, how come it only rebuilt /dev/md0?
So md1/md2 was NOT rebuilt?
Correct.
quoted
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.
quoted
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..
quoted
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.
On Dec 1 2007 07:12, Justin Piszcz wrote:
On Sat, 1 Dec 2007, Jan Engelhardt wrote:
quoted
On Dec 1 2007 06:19, Justin Piszcz wrote:
quoted
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 :)
LILO cares much less about disk layout / filesystems than GRUB does,
so I would have expected LILO to cope with all sorts of superblocks.
OTOH I would suspect GRUB to only handle 0.90 and 1.0, where the MDSB
is at the end of the disk <=> the filesystem SB is at the very beginning.
quoted
quoted
So two questions:
1) If it rebuilt by itself, how come it only rebuilt /dev/md0?
So md1/md2 was NOT rebuilt?
Correct.
Well it should, after they are readded using -a.
If they still don't, then perhaps another resync is in progress.
On Sat, 1 Dec 2007, Jan Engelhardt wrote:
On Dec 1 2007 07:12, Justin Piszcz wrote:
quoted
On Sat, 1 Dec 2007, Jan Engelhardt wrote:
quoted
On Dec 1 2007 06:19, Justin Piszcz wrote:
quoted
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 :)
LILO cares much less about disk layout / filesystems than GRUB does,
so I would have expected LILO to cope with all sorts of superblocks.
OTOH I would suspect GRUB to only handle 0.90 and 1.0, where the MDSB
is at the end of the disk <=> the filesystem SB is at the very beginning.
quoted
quoted
quoted
So two questions:
1) If it rebuilt by itself, how come it only rebuilt /dev/md0?
So md1/md2 was NOT rebuilt?
Correct.
Well it should, after they are readded using -a.
If they still don't, then perhaps another resync is in progress.
There was nothing in progress, md0 was synced up and md1,md2 = degraded.