Hello all,
I am gradually getting through the process of setting up a partitioned
RAID1 array, but having quite a time with it.
I applied Neil Brown's md-partitioning patches to my 2.4.18 kernel, and
embarked on the journey.
I'm trying to get a pair of 40GB ATA100 IDE drives to work as a bootable
RAID1 array, as an mdp-type md device.
I'm actually getting pretty close now, I just can't get LILO (22.3.2) to
write the boot sector to the array drives, pretty much any way I try to
do it.
I'm not running /dev file system, since I've never been able to get that
to work with my Red hat systems (though it seems like it would be really
neat, if my systems wouldn't lock up after compiling a kernel with that
feature enabled. Are you supposed to delete all the entries in /dev,
leaving just the /dev mount point, and let the kernel fill in the
entries for you?).
So I had to manually create the devices. I'll spare all the gruesome
details of incorrect device names made along the way, experimenting with
major and minor device numbers, etc.
Here's what I have under my /dev device tree for md-type entries:
(The first group, /dev/mdXX, were already there, I had to create the
rest by hand. Well... by script... ;)
Can somebody who actually has this working (particularly if you were
able to get LILO to write a boot record to the drives somehow) take a
look at this list of devices and let me know what else needs to be
listed under /dev? From reading Neil's posts on the list, I may need
md0p1 - md0p15 devices, etc., but not sure whether I should use major 9
or major 60 for these.
MAIN md DEVICE NUMBERS
PERMS
UID GID MAJOR#
MINOR#
DEVICE
=================================================
brw-rw-- root disk 9 0 /dev/md0
brw-rw-- root disk 9 1 /dev/md1
...
brw-rw-- root disk 9 31 /dev/md31
PARTITIONED MD DEVICES --
ASSIGNED sdX/hdX-STYLE DEVICE ID'S AND PARTITION #'S BY THE KERNEL WHEN
THE md DEVICE STARTS - USE THIS DEVICE ID (/dev/mda, /dev/mdb) IN FDISK
(I had to make these by hand -- a 'cat /proc/devices' showed the device
major number to be 60 for the mdp device on this machine)
PERMS
UID GID MAJOR#
MINOR#
DEVICE
=================================================
brw-rw-- root disk 60 0 /dev/mda
brw-rw-- root disk 60 1 /dev/mda1
...
brw-rw-- root disk 60 15 /dev/mda15
(you would also need a set of /dev/mdb device numbers if you had a
second partitioned md device, but I only have an mda right now):
PERMS
UID GID MAJOR#
MINOR#
DEVICE
=================================================
brw-rw-- root disk 60 16 /dev/mdb
brw-rw-- root disk 60 17 /dev/mdb1
...
brw-rw-- root disk 60 31 /dev/mdb15
MDP-TYPE DEVICE AND PARTITION NUMBERS
I was starting to think I wouldn't need these until I actually got ext3
filesystems created on the partitions, and booted up with these
filesystems listed in /etc/fstab - journald apparently looks for these
device names when starting the journals, per dmesg output. But notice
that the major and minor numbers are the same as used in the mdaXX
devices above.
PERMS
UID GID MAJOR#
MINOR#
DEVICE
=================================================
brw-rw-- root disk 60 0 /dev/mdp0
brw-rw-- root disk 60 1 /dev/mdp0p1
...
brw-rw-- root disk 60 15 /dev/mdp0p15
this would be for a 2nd partitioned md device, like mdb above:
brw-rw-- root disk 60 16 /dev/mdp1
brw-rw-- root disk 60 17 /dev/mdp1p1
...
brw-rw-- root disk 60 31 /dev/mdp1p15
INTERESTING OBSERVATIONS SO FAR
1. Once you create the raid device ('mkraid /dev/md0') or otherwise
start it, it is interesting that the drive geometry displays differently
depending on whether you start fdisk with /dev/md0 or /dev/mda. I
finally realized that 'fdisk /dev/mda' is the logical way to do it,
since the C/H/S displayed matches what the kernel sees the geometry to
be on the pair of actual drives when the EIDE driver initializes. But
if you try to view a partition table you created under one device name,
from the other device name, you'll probably see error messages about the
partitions not ending on cylinder boundaries. Creating the partition
table with /dev/mda as the device name to launch with made the most
sense, assuming the OS/kernel will talk to this drive as /dev/mda, and
ext3 seems to like it just fine.
UP TO THIS POINT
By using an 'md=0,/dev/hde,/dev/hdg' added to the Grub command line for
the kernel, the RAID1 array starts fine, and it will mount all the ext3
filesystems I created partitions for on the mda device (since I have
them all in /etc/fstab now, under a /ideraid mount point off the root fs
on the main storage for the machine).
I did not have any luck with changing the partition types to FD for
autodetection (it kept complaining about invalid superblocks) and was
glad to find a good commandline example of manually specifying your md
arrays on the kernel cmdline, in a previous post to the list.
PROBLEMS I CAN'T FIGURE OUT (HELP!!!)
LILO NOT COOPERATING
LILO 22.3.2 doesn't seem to like /dev/md0 as the boot= and disk= device.
Or /dev/mda, or /dev/mdp0 either. I can specify /dev/hde or /dev/hdg
(the actual IDE drives the RAID1 array is made of), but LILO won't
consider it a RAID device in that case, and I didn't think you were
supposed to try to write directly to a RAID member device by it's
"direct name".
I also tried specifying /dev/mda1 (what will be the new /boot partition,
marked bootable in partition table), but it still says 'Fatal: Not a
partition name; no digits at the end'.
Currently the md0/mda partitioned RAID1 array is an add-on - I am using
a large external SCSI-to-ATA100 RAID subsystem, which has a giant RAID5
array presented as one big drive with 3 partitions - /dev/sda1 (/boot),
/dev/sda2 (/), and /dev/sda3 (swap). I'm trying to get everything moved
over to this RAID1 pair of drives, but I want to make sure I can BOOT
from the RAID1 md0/mda pair before I actually move everything over. So
in the meantime, I have a mountpoint on the main root fs called
/ideraid, which is how I have mounted all the partitions of the md0/mda
RAID1 array to experiment with.
If anybody (Neil?) can offer some advice on how to get LILO to write a
boot sector to the RAID1 array pair, it would be greatly appreciated. I
am so close to getting this working!!!
I'm tempted to try stopping the md0 raid device, and fixing up lilo.conf
to install LILO on /dev/hde (disk=/dev/hde and boot=/dev/hde), then
start the array again and see if it can just sync the MBR/boot record
from one drive to the other.
thanks,
vinnie
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