CentOS - Jan 2017 - CentOS 7 install on one RAID 1 [not-so-SOLVED]

On 01/24/17 19:00, Gordon Messmer wrote:
> On 01/24/2017 02:14 PM, m.roth at 5-cent.us wrote:
>> So, it installed happily.
>> Then wouldn't boot.
>
> What did the storage configuration look like, exactly?  I'd guess that
you put
> one partition on each disk, combined those in a RAID1 MD array, made than
an
> LVM physical volume, and then created filesystems and swap on LVs.  But
that's
> a lot of guesses.  Did you use MBR partitions or GPT?  Are you booting
under
> BIOS or UEFI?  Where do your partitions start?  Did you create a standard
MD
> RAID volume and LVM or a partitionable RAID volume and partitions?
No. Brand new machine, pulled it out of the box and racked it. NOTHING on the 
internal SSDs. Made an md RAID 0 on the raw disks - /dev/sda /dev/sdb. No 
partitions, nothing. However, when I bring it up, fdisk shows an MBR with no 
partitions. I can, however, mount /dev/md127p3 as /mnt/sysimage, and all is
there.

Did I need to make a single partition, on each drive, and then make the RAID 1 
out of *those*? I don't think I need to have /boot not on a RAID.

	mark

You didn't answer all of the questions I asked, but I'll answer as best 
I can with the information you gave.

On 01/25/2017 04:47 AM, mark wrote:
>
> Made an md RAID 0 on the raw disks - /dev/sda /dev/sdb. No partitions, 
> nothing.
OK, so right off the bat we have to note that this is not a 
configuration supported by Red Hat.  It is possible to set such a system 
up, but it may require advanced knowledge of grub2 and mdadm.  Because 
the vendor doesn't support this configuration, and as you've seen, the 
tools don't always parse out the information they need, you'll forever 
be responsible for fixing any boot problems that come up.  Do you really 
want that?

I sympathize.  I wanted to use full disk RAID, too.  I thought that 
replacing disks would be much easier this way, since there'd just be one 
md RAID device to manage.  That was an attractive option after working 
with hardware RAID controllers that were easy to manage but expensive, 
unreliable, and performed very poorly in some conditions.  But after a 
thorough review, I found my earlier suggestion of partitioned RAID with 
the kickstart and RAID management script I provided was the least work 
for me, in the long term.
> However, when I bring it up, fdisk shows an MBR with no partitions. I 
> can, however, mount /dev/md127p3 as /mnt/sysimage, and all is there.
I assume you're booting with BIOS, then?

One explanation for fdisk showing nothing is that you're using GPT 
instead of MBR (I think).  In order to boot on such a system, you'd need 
a bios_boot partition at the beginning of the RAID volume to provide 
enough room for grub2 not to stomp on the first partition with a filesystem.

The other explanation that comes to mind is that you're using an mdadm 
metadata version stored at the beginning of the drive instead of the 
end.  Do you know what metadata version you used?
> Did I need to make a single partition, on each drive, and then make 
> the RAID 1 out of *those*? I don't think I need to have /boot not on a 
> RAID.

That's one option, but it still won't be a supported configuration.

Gordon Messmer wrote:
> You didn't answer all of the questions I asked, but I'll answer as
best
> I can with the information you gave.
>
Manitu ate my email, *again*.
> On 01/25/2017 04:47 AM, mark wrote:
>>
>> Made an md RAID 0 on the raw disks - /dev/sda /dev/sdb. No partitions,
>> nothing.
>
> OK, so right off the bat we have to note that this is not a
> configuration supported by Red Hat.  It is possible to set such a system
> up, but it may require advanced knowledge of grub2 and mdadm.  Because
<snip>
> I sympathize.  I wanted to use full disk RAID, too.  I thought that
<snip>
Thank you.
>
>> However, when I bring it up, fdisk shows an MBR with no partitions. I
>> can, however, mount /dev/md127p3 as /mnt/sysimage, and all is there.
>
> I assume you're booting with BIOS, then?
Yup.
>
> One explanation for fdisk showing nothing is that you're using GPT
> instead of MBR (I think).  In order to boot on such a system, you'd
need
Nope. fdisk sees it as an MBR. The SSDs are only 128G. They just run the
server, and the LSI card takes care of the 12 hot-swap drives.... <g>
(It's a storage server.)
> a bios_boot partition at the beginning of the RAID volume to provide
> enough room for grub2 not to stomp on the first partition with a
> filesystem.
>
> The other explanation that comes to mind is that you're using an mdadm
> metadata version stored at the beginning of the drive instead of the
> end.  Do you know what metadata version you used?
I took CentOS 7's default for mdadm.
>
>> Did I need to make a single partition, on each drive, and then make
>> the RAID 1 out of *those*? I don't think I need to have /boot not
on a
>> RAID.
>
> That's one option, but it still won't be a supported configuration.
Yeah, I see. Well, time to go rebuild, and this time with three separate
RAID 1 partitions....

        mark