Jonathan Vomacka wrote:
> CentOS Community,
>
> I have a dedicated server with 4 hard drives in a RAID 10 software
> configuration running LVM. My OS is CentOS 6.2. Earlier today, I
> rebooted my system and my system did not come back online. I opened a
> ticket with my datacenter who informed me that one of my hard drives is
> no longer recognized by the bios and has failed. I was told that an OS
> reinstall was needed.
>
> I don't understand why a reinstall would be necessary when the drives
> are in RAID 10. Apparently when the datacenter did the initial OS
> install, they ONLY installed the MBR on one drive instead of all 4
> leaving the other 3 drives unbootable.
<snip>
Whatever the outcome, I would strongly recommend escalating this to a
manager, since the staff installed it incorrectly - perhaps they don't
understand what a RAID is? But they need to make this right - you're
paying for it.

Besides, it's not Windows....

mark

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On 03/02/2012 09:03 AM, Jonathan Vomacka wrote:
> CentOS Community,
>
> I have a dedicated server with 4 hard drives in a RAID 10 software
> configuration running LVM. My OS is CentOS 6.2. Earlier today, I
> rebooted my system and my system did not come back online. I opened a
> ticket with my datacenter who informed me that one of my hard drives is
> no longer recognized by the bios and has failed. I was told that an OS
> reinstall was needed.
>
> I don't understand why a reinstall would be necessary when the drives
> are in RAID 10. Apparently when the datacenter did the initial OS
> install, they ONLY installed the MBR on one drive instead of all 4
> leaving the other 3 drives unbootable.
>
> Is this a way to salvage this with a liveCD without having to reload the
> OS? This server is a very important mail server running OpenLDAP and
> MySQL. I figured maybe I could install the MBR using a liveCD which may
> fix the system.
>
> If an OS reload is the ONLY option, is there a way to reload it without
> touching the /var or /opt filesystems? (yes they were created as a
> seperate partition) however I am not sure if OpenLDAP or MySQL installs
> anything to /usr which I would be completely screwed...
>
> Please help

Advice provided as-is.

Boot from a live CD using the CentOS 6.2 install media. Once booted:

<bash># grub
<grub> root (hd0,0)
<grub> setup (hd0)
<grub> root (hd1,0)
<grub> setup (hd1)
<grub> root (hd2,0)
<grub> setup (hd2)
<grub> quit
<bash># reboot

This assumes that grub sees the drives at '0, 1 and 2' and the boot
partition is the first on each drive. If it is, when you type 'root
(hdX,0)' it should report that a file system was found. The 'setup
(hdX)' will tell grub to write the MBR to the specified disk.

--
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E-Mail: digimer@alteeve.com
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Digimer wrote:
<snip>
> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>
> <bash># grub
> <grub> root (hd0,0)
> <grub> setup (hd0)
> <grub> root (hd1,0)
> <grub> setup (hd1)
> <grub> root (hd2,0)
> <grub> setup (hd2)
> <grub> quit
> <bash># reboot
>
> This assumes that grub sees the drives at '0, 1 and 2' and the boot
> partition is the first on each drive. If it is, when you type 'root
> (hdX,0)' it should report that a file system was found. The 'setup
> (hdX)' will tell grub to write the MBR to the specified disk.

THANK YOU! I could have used that once or twice, and had no idea that grub
could create a std. MBR.

mark

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On 03/02/2012 01:01 PM, m.roth@5-cent.us wrote:
> Digimer wrote:
> <snip>
>> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>>
>> <bash># grub
>> <grub> root (hd0,0)
>> <grub> setup (hd0)
>> <grub> root (hd1,0)
>> <grub> setup (hd1)
>> <grub> root (hd2,0)
>> <grub> setup (hd2)
>> <grub> quit
>> <bash># reboot
>>
>> This assumes that grub sees the drives at '0, 1 and 2' and the boot
>> partition is the first on each drive. If it is, when you type 'root
>> (hdX,0)' it should report that a file system was found. The 'setup
>> (hdX)' will tell grub to write the MBR to the specified disk.
>
> THANK YOU! I could have used that once or twice, and had no idea that grub
> could create a std. MBR.
>
> mark

I've run into this a few times now where RAID'ed /boot doesn't have the
MBR written to all members. I've now gotten into the habit of running
this after OS install. I should file a bug with upstream...

--
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On 3/2/2012 1:01 PM, m.roth@5-cent.us wrote:
> Digimer wrote:
> <snip>
>> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>>
>> <bash># grub
>> <grub> root (hd0,0)
>> <grub> setup (hd0)
>> <grub> root (hd1,0)
>> <grub> setup (hd1)
>> <grub> root (hd2,0)
>> <grub> setup (hd2)
>> <grub> quit
>> <bash># reboot
>>
>> This assumes that grub sees the drives at '0, 1 and 2' and the boot
>> partition is the first on each drive. If it is, when you type 'root
>> (hdX,0)' it should report that a file system was found. The 'setup
>> (hdX)' will tell grub to write the MBR to the specified disk.
> THANK YOU! I could have used that once or twice, and had no idea that grub
> could create a std. MBR.

When I set up a RAID 1, I do it like this:

device (hd0) /dev/sda
root (hd0,0)
setup (hd0)
device (hd0) /dev/sdb
root (hd0,0)
setup (hd0)
device (hd0) /dev/sdc
root (hd0,0)
setup (hd0)

This way, all the drives are set up as if they are hd0. This way, any
of them will boot normally as a stand-alone drive.

--
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On 03/02/2012 02:39 PM, Digimer wrote:
> On 03/02/2012 01:01 PM, m.roth@5-cent.us wrote:
>> Digimer wrote:
>> <snip>
>>> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>>>
>>> <bash># grub
>>> <grub> root (hd0,0)
>>> <grub> setup (hd0)
>>> <grub> root (hd1,0)
>>> <grub> setup (hd1)
>>> <grub> root (hd2,0)
>>> <grub> setup (hd2)
>>> <grub> quit
>>> <bash># reboot
>>>
>>> This assumes that grub sees the drives at '0, 1 and 2' and the boot
>>> partition is the first on each drive. If it is, when you type 'root
>>> (hdX,0)' it should report that a file system was found. The 'setup
>>> (hdX)' will tell grub to write the MBR to the specified disk.
>>
>> THANK YOU! I could have used that once or twice, and had no idea that grub
>> could create a std. MBR.
>>
>> mark
>
> I've run into this a few times now where RAID'ed /boot doesn't have the
> MBR written to all members. I've now gotten into the habit of running
> this after OS install. I should file a bug with upstream...
>

https://bugzilla.redhat.com/show_bug.cgi?id=799501

--
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Putting an MBR on all disks right after an OS install, as previously
mentioned, is of course the best option (although it's too late for that
in this instance). Others have talked about using the live CD to
recover from your situation, which is good.

Other, "less good" options that might be available to you are:
- change the boot device in the BIOS
- if the server isn't capable of doing that, have them
flip the cables.

I, also, would recommend having a little chat with their manager ...

Devin

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Digimer! Thanks for the info. Since the HDD0 drive is completely failed,
I would need to replace it.. it doesn't have any data on it. The other
three HDD's would need the MBR. I am assuming... that because RAID 10
means Striped+Mirroring that HDD 3+4 would be mirrored and 1+2 would be
mirrored... is this an accurate statement?

On 3/2/2012 12:07 PM, Digimer wrote:
> On 03/02/2012 09:03 AM, Jonathan Vomacka wrote:
>> CentOS Community,
>>
>> I have a dedicated server with 4 hard drives in a RAID 10 software
>> configuration running LVM. My OS is CentOS 6.2. Earlier today, I
>> rebooted my system and my system did not come back online. I opened a
>> ticket with my datacenter who informed me that one of my hard drives is
>> no longer recognized by the bios and has failed. I was told that an OS
>> reinstall was needed.
>>
>> I don't understand why a reinstall would be necessary when the drives
>> are in RAID 10. Apparently when the datacenter did the initial OS
>> install, they ONLY installed the MBR on one drive instead of all 4
>> leaving the other 3 drives unbootable.
>>
>> Is this a way to salvage this with a liveCD without having to reload the
>> OS? This server is a very important mail server running OpenLDAP and
>> MySQL. I figured maybe I could install the MBR using a liveCD which may
>> fix the system.
>>
>> If an OS reload is the ONLY option, is there a way to reload it without
>> touching the /var or /opt filesystems? (yes they were created as a
>> seperate partition) however I am not sure if OpenLDAP or MySQL installs
>> anything to /usr which I would be completely screwed...
>>
>> Please help
>
> Advice provided as-is.
>
> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>
> <bash># grub
> <grub> root (hd0,0)
> <grub> setup (hd0)
> <grub> root (hd1,0)
> <grub> setup (hd1)
> <grub> root (hd2,0)
> <grub> setup (hd2)
> <grub> quit
> <bash># reboot
>
> This assumes that grub sees the drives at '0, 1 and 2' and the boot
> partition is the first on each drive. If it is, when you type 'root
> (hdX,0)' it should report that a file system was found. The 'setup
> (hdX)' will tell grub to write the MBR to the specified disk.
>
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On Fri, Mar 02, 2012 at 09:03:44AM -0500, Jonathan Vomacka wrote:
> CentOS Community,
>
> I have a dedicated server with 4 hard drives in a RAID 10 software
> configuration running LVM. My OS is CentOS 6.2. Earlier today, I
> rebooted my system and my system did not come back online. I opened a
> ticket with my datacenter who informed me that one of my hard drives is
> no longer recognized by the bios and has failed. I was told that an OS
> reinstall was needed.

how was your disks partitions? and how was the lvm setup?
was /boot made of a mdadm raid1 array?

there is a dracut issue on raid1 array (fixed by now, if you updated
to the latest dracut release and rebuild your initramfs):
http://bugs.centos.org/view.php?id=5400

Btw the anaconda installer does install grub on the MBR of both raid1 members.
No idea if it does so for lvm over raid10 array.

Tru

--
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On 3/2/2012 2:46 PM, Bowie Bailey wrote:
> On 3/2/2012 1:01 PM, m.roth@5-cent.us wrote:
>> Digimer wrote:
>> <snip>
>>> Boot from a live CD using the CentOS 6.2 install media. Once booted:
>>>
>>> <bash># grub
>>> <grub> root (hd0,0)
>>> <grub> setup (hd0)
>>> <grub> root (hd1,0)
>>> <grub> setup (hd1)
>>> <grub> root (hd2,0)
>>> <grub> setup (hd2)
>>> <grub> quit
>>> <bash># reboot
>>>
>>> This assumes that grub sees the drives at '0, 1 and 2' and the boot
>>> partition is the first on each drive. If it is, when you type 'root
>>> (hdX,0)' it should report that a file system was found. The 'setup
>>> (hdX)' will tell grub to write the MBR to the specified disk.
>> THANK YOU! I could have used that once or twice, and had no idea that grub
>> could create a std. MBR.
>
> When I set up a RAID 1, I do it like this:
>
> device (hd0) /dev/sda
> root (hd0,0)
> setup (hd0)
> device (hd0) /dev/sdb
> root (hd0,0)
> setup (hd0)
> device (hd0) /dev/sdc
> root (hd0,0)
> setup (hd0)
>
> This way, all the drives are set up as if they are hd0. This way, any
> of them will boot normally as a stand-alone drive.
>

Bowie, in terms of RAID 10, each drive technically cant be standalone
right? The drives are striped and mirrored.
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