Need help creating a software raid array.

Thaidog · #1 8th March 2009, 12:30 AM

I am following a Gentoo howto to create a software raid 0 arrary, but when I reboot the array is gone:

http://hilli.dk/howtos/lvm2-and-software-raid-in-linux/

Fecora 10 does not seem to have the /etc/mdadm.conf file that save the config with:

Update /etc/mdadm.conf with

# mdadm --detail --scan >> /etc/mdadm.conf

How do I save the raid array on FC 10?

marcrblevins · #2 8th March 2009, 12:07 PM

Code:

man mdadm

While in there, type:

Code:

/EXAMPLES

Has good examples there.

Thaidog · #3 8th March 2009, 04:45 PM

Quote:

Originally Posted by marcrblevins

Code:

man mdadm

While in there, type:

Code:

/EXAMPLES

Has good examples there.

Strange... i read the man examples but my system stil does not seem to have the mdadm.conf file;

then I do a updatedb && locate mdadm.conf

[root@iccproject tylerm]# updatedb
[root@iccproject tylerm]# locate mdadm.conf
/home/tylerm/mdadm.conf
/usr/share/doc/mdadm-2.6.7.1/mdadm.conf-example
/usr/share/man/man5/mdadm.conf.5.gz
[root@iccproject tylerm]# cat /home/tylerm/mdadm.conf
’DEVICE /dev/hd*[0-9] /dev/sd*[0-9]’
[root@iccproject tylerm]#

That does not seem like the right place for that file... and the array is ggone again after reboot.

notageek · #4 8th March 2009, 06:27 PM

You'll have to manually write /etc/mdadm.conf

Example:

Code:

ARRAY /dev/md0 level=linear num-devices=2 devices=/dev/sdb1,/dev/sdb2

man page of mdadm.conf has got examples that you can try.

Thaidog · #5 9th March 2009, 12:07 AM

Quote:

Originally Posted by notageek

You'll have to manually write /etc/mdadm.conf

Example:

Code:

ARRAY /dev/md0 level=linear num-devices=2 devices=/dev/sdb1,/dev/sdb2

man page of mdadm.conf has got examples that you can try.

Ok, so I read the man page and tried two configs but still nothing:

The configs I tried:
[root@iccproject tylerm]# cat /etc/mdadm.conf
ARRAY /dev/md1 UUID=67c91b6c-9c80-af3f-aeff-096bf1e86363

[root@iccproject tylerm]# cat /etc/mdadm.conf
ARRAY /dev/md1 level=lraid0 num-devices=2 devices=/dev/sdb1,/dev/sdc1

Here is the UUID list that shows sdc1 and sdb1 as the same UUID:

[root@iccproject tylerm]# lsmod | grep md
[root@iccproject tylerm]# blkid
/dev/mapper/VolGroup00-LogVol00: UUID="9b39fee7-7b3d-4ac5-a9a1-5ceddf4cb5fb" TYPE="xfs"
/dev/mapper/VolGroup00-LogVol01: TYPE="swap" UUID="da557042-0c61-4cec-ab01-e52cde00ed54"
/dev/sda1: LABEL="/boot" UUID="bfae2cca-6434-4039-aa35-cbc5e1d525ce" TYPE="ext3" SEC_TYPE="ext2"
/dev/sda2: UUID="sZN5vY-f58K-MKlY-CAtn-YIdb-g4j7-GJiAEP" TYPE="lvm2pv"
/dev/VolGroup00/LogVol00: UUID="9b39fee7-7b3d-4ac5-a9a1-5ceddf4cb5fb" TYPE="xfs"
/dev/VolGroup00/LogVol01: TYPE="swap" UUID="da557042-0c61-4cec-ab01-e52cde00ed54"
/dev/sdb1: UUID="67c91b6c-9c80-af3f-aeff-096bf1e86363" TYPE="mdraid"
/dev/sdc1: UUID="67c91b6c-9c80-af3f-aeff-096bf1e86363" TYPE="mdraid"
/dev/sde1: LABEL="USB20FD" UUID="8C14-6402" TYPE="vfat"
[root@iccproject tylerm]# cat /etc/mdadm.conf
ARRAY /dev/md1 UUID=67c91b6c-9c80-af3f-aeff-096bf1e86363

lsmod doees not show "md" to be loaded like the mdadm.conf man pages says that it uses md as the driver.

[root@iccproject tylerm]# modprobe md
FATAL: Module md not found

Then I tired the The gentoo raid dirver name:
[root@iccproject tylerm]# modprobe dm-mod
FATAL: Module md not found

fdisk -l shows the disks:

Code:

Disk /dev/sdb: 150.0 GB, 150039945216 bytes
255 heads, 63 sectors/track, 18241 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x1ad5a23a

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       18241   146520801   83  Linux

Disk /dev/sdc: 150.0 GB, 150039945216 bytes
255 heads, 63 sectors/track, 18241 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00008612

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1       18241   146520801   83  Linu

I fired up the LVM2 gui and no volume group but the root filesystem (the volume group should be /dev/vg/xfsstripe)

Finally here is the scan from mdadm:

[root@iccproject tylerm]# mdadm --detail --scan
mdadm: md device /dev/md/d0 does not appear to be active.
mdadm: md device /dev/md/d1 does not appear to be active.

Any ideas?

Thaidog · #6 9th March 2009, 01:00 AM

Ok so I got the volume to be found by mdadm finally - this is what I needed:

[root@iccproject tylerm]# mdadm --examine --scan
ARRAY /dev/md0 level=raid0 num-devices=2 UUID=1b9a0101:475f34c9:8121eaed:ec72a205
ARRAY /dev/md1 level=raid0 num-devices=2 UUID=6c1bc967:3faf809c:6b09ffae:6363e8f1

The UUID for md1 and md0 is different form the UUID that identifies sdc and sdb

i changed it to the md1 UUID and now the raid volus is said to be active:

[root@iccproject tylerm]# mdadm --detail --scan
mdadm: md device /dev/md/d0 does not appear to be active.
ARRAY /dev/md1 level=raid0 num-devices=2 metadata=0.90 UUID=6c1bc967:3faf809c:6b09ffae:6363e8f1

Unfortunately the LVM is not being seen now:

[root@iccproject tylerm]# mdadm -As /dev/md1
mdadm: device /dev/md1 already active - cannot assemble it
[root@iccproject tylerm]# mdadm -E /dev/md1
mdadm: No md superblock detected on /dev/md1.

not sure but i think that the system is confused now since I initialized the drive set twice (md0 and md1)

Not sure what to do about that.

notageek · #7 9th March 2009, 05:54 AM

This does seem confusing.

Few things that I noted was your partitions sdb1 and sdc1 are not set to type "Linux raid auto detect", ideally thats what they should be. Use fdisk and then type "t", the codes for "Linux raid auto detect" is "fd"

Then I see that the syntax for mdadm.conf should contain the array (device) name and the constituting devices. Stick with device names (/dev/sdb etc) UUIDs are confusing.

I did not follow the LVM thing.

Thaidog · #8 9th March 2009, 06:35 PM

Any ideas on who to delete these two arrays so they do not show up when I issue:

[root@iccproject tylerm]# mdadm --examine --scan
ARRAY /dev/md0 level=raid0 num-devices=2 UUID=1b9a0101:475f34c9:8121eaed:ec72a205
ARRAY /dev/md1 level=raid0 num-devices=2 UUID=6c1bc967:3faf809c:6b09ffae:6363e8f1

notageek · #9 10th March 2009, 05:09 AM

Few steps:

1. Stop the raid array (in your case all of them)

Code:

mdadm --stop --scan

2. Fail the disk and remove it from the array

Code:

  mdadm /dev/md0 -f /dev/sda1 -r /dev/sda1 -a /dev/sda1

Where '-f' is for failing a disk, '-r' to remove, '-a' auto

3. Remove the config from /etc/mdadm.conf

Edit: I thought you want to destroy the raid devices, if that's not what you want then removing config from /etc/mdam.conf will get you the desired result.