[CentOS] looking for RAID 1+0 setup instructions?

Ross Walker rswwalker at gmail.com
Tue Sep 1 16:04:14 UTC 2009


On Tue, Sep 1, 2009 at 9:44 AM, Ross Walker<rswwalker at gmail.com> wrote:
> On Aug 31, 2009, at 7:59 PM, Christopher Chan
> <christopher.chan at bradbury.edu.hk> wrote:
>
>> Ross Walker wrote:
>>>
>>> Problem is the install program doesn't support setting up RAID10 or
>>> layered MD devices.
>>>
>> Oh? I have worked around it before even in the RH9 days. Just go into
>> the shell (Hit F2), create what you want, go back to the installer. Are
>> you so sure that anaconda does not support creating layered md devices?
>> BTW, why are you talking about md devices now? I thought you said md and
>> dm are the same?
>
> You know what, let me try just that today, I have a new install to do, so
> I'll try pre-creating a RAID10 on install and report back. First I'll try
> layered MD devices and then I'll try creating a RAID10 md device and we'll
> see if it can even boot off them.

Ok, I verified that inside anaconda one cannot create layered MD RAID
arrays because once one forms an array there is no choice to create a
volume of type "Software RAID". The RAID choices are RAID0, RAID1,
RAID5 or RAID6 during install, no RAID10.

I can create multiple RAID1s though, of type "LVM Physical Volume" and
then create a volume group composed of those. I can then create a root
LV and a swap LV, though these will not be striped because LVM doesn't
default to striping PVs, but concatenating, so in order to stripe
these I'll need to leave enough free space to create striped versions,
dump and restore from the old root to the new root and then edit the
fstab/grub, run mkinitrd and reboot. Not exactly convenient, but
unfortunate due to LVM's default policy of concatenating PVs instead
of striping them... oh well.

As far as creating a RAID10 at the command prompt, the dm-raid10
kernel module is missing from the install image, so no luck directly
creating a RAID10, and after a couple of reboots I was able to create
a layered setup, but anaconda didn't recognize it (either immediately,
or after a reboot) to be able to perform an install on it because it
doesn't start the arrays upon startup to be able to find the nested
one.

So if it worked for you in RH9, it no longer works anymore.

Maybe because RH9 had a separate MD RAID implementation and not the
device-mapper implementation.

-Ross



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