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Unable to create partitionable Raid1

Posted: 2011/08/16 20:20:25
by bearbo
Hello,

I previously was able to install CentOS 5 on a partitionable raid1 following this instruction:http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1.

Recently, I just installed a CentOS 6 on a new system, and was trying to follow the same instruction, but was stuck at step 5. When I tried to mount the array using:

bash-4.1# mount /dev/md_d0p1 /mnt/sysimage
mount: you must specify the filesystem type

Earlier in the process, when I was creating the raid, mdadm was complaining that a partition table already existed on /dev/sda:

bash-4.1# mdadm --create --level=1 --raid-devices=2 /dev/md_d0 /dev/sda missing
mdadm: partition table exists on /dev/sda but will be lost or meangless after creating array
mdadm: Note: this array ahs metadata ath the start and may not be suitable as a boot device. If you plan to store '/boot' on this device please ensure that your boot-loader understand md/v1.x metadata, or use --metadata=0.98
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md_d0 started
bash-4.1#

I don't know if these two are related.

Any help is appreciated!!

Unable to create partitionable Raid1

Posted: 2011/08/17 01:06:09
by WhatsHisName
Have not looked into it, but I assume mdadm natively supports partitionable arrays under EL6.

From the madam manpage:

[quote]-a, --auto{=yes,md,mdp,part,p}{NN}

Instruct mdadm how to create the device file if needed, possibly allocating an unused minor number. "md" causes a non-partitionable array to be used ([b]though since Linux 2.6.28, these array devices are in fact partitionable[/b]). "mdp", "part" or "p" causes a partitionable array (2.6 and later) to be used. "yes" requires the named md device to have a Â’standardÂ’ format, and the type and minor number will be determined from this. With mdadm 3.0, device creation is normally left up to udev so this option is unlikely to be needed.[/quote]
Reviewing the [url=http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html-single/6.1_Technical_Notes/index.html]RHEL 6.1 Technical Notes[/url], I see no specific mention of the feature.

Re: Unable to create partitionable Raid1

Posted: 2011/08/17 16:46:44
by bearbo
As I mentioned, I was able to follow those instruction under CentOS 5.5. Is there any reason (or indication) that the feature was removed?

Re: Unable to create partitionable Raid1

Posted: 2011/08/18 18:33:55
by bearbo
Bump. Please help!

Re: Unable to create partitionable Raid1

Posted: 2011/08/22 17:09:12
by bearbo
I was able to create the array with the "--metadata=0.98" option and mount it. However I'm encountering more problems :-(

When I tried to patch the mkinitrd, I got this error:
patching file mkinitrd
Hunk #1 FAILED at 420.
Hunk #2 FAILED at 611.
Hunk #3 FAILED at 635.
Hunk #4 FAILED at 1703.
4 out of 4 hunks FAILED -- saving rejects to file mkinitrd.rej

Is patching of mkinitrd still necessary? Even without successful patch of mkinitrd, I seem to be able to boot with md_d0, which looks promising. But upon booting, mdadm --detail /dev/_md_d0 shows this:
/dev/md_d0:
Version : 0.90
Creation Time : Sat Aug 20 01:25:39 2011
Raid Level : raid1
Array Size : 488386496 (465.76 GiB 500.11 GB)
Used Dev Size : 488386496 (465.76 GiB 500.11 GB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Sun Aug 21 09:38:47 2011
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0

UUID : 3cbc70d5:a3d81de3:bfe78010:bc810f04
Events : 0.239

Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 0 0 1 removed

It seems to think that /dev/sdb is removed, for whatever reason.

I don't know if the two issues are linked, but any help is very appreciated!