[CentOS] Re: Anaconda doesn't support raid10

Fri May 11 19:30:39 UTC 2007
Ross S. W. Walker <rwalker at medallion.com>

> -----Original Message-----
> From: centos-bounces at centos.org 
> [mailto:centos-bounces at centos.org] On Behalf Of Ruslan Sivak
> Sent: Friday, May 11, 2007 3:27 PM
> To: CentOS mailing list
> Subject: Re: [CentOS] Re: Anaconda doesn't support raid10
> 
> Chris Croome wrote:
> > Hi
> >
> > On Fri 11-May-2007 at 09:38:22AM -0400, Ross S. W. Walker wrote:
> >   
> >>> The entire use all four disks for /boot makes no sense if 
> two disks
> >>> belonging to the same mirror for the lvm go down. Please stop this
> >>> nonsense about surviving everything to no benefit. You can have
> >>> three disks fail and still have a working /boot. For what?
> >>>       
> >> I think the idea of the 4 partition raid1 was more of, 
> what else is he
> >> going to do with the 200MB at the beginning of each disk 
> which he has
> >> because of partition symmetry across drives?
> >>
> >> Makes sense to just dup the partition setup from one to 
> the other and
> >> now with grub and a working /boot on each disk the order 
> of the drives
> >> is no longer important, he can take all 4 out, play 4 disk 
> monty, slap
> >> them back in and the system should come up without a problem.
> >>     
> >
> > FWIW this is what I did with the last server I built which 
> had 4x500gb
> > drives -- a RAID 1 /boot on 4 drives. The trick for this is 
> to edit your
> > grub.conf so that you can boot off any drive and run 
> grub-install on all
> > 4 drives, also you have to remember to manually edit your grub.conf
> > after each kernel upgrade to add the 3 extra disks:
> >
> >  title CentOS (2.6.18-8.1.1.el5xen) Disk 0
> >          root (hd0,0)
> >          kernel /xen.gz-2.6.18-8.1.1.el5
> >          module /vmlinuz-2.6.18-8.1.1.el5xen ro 
> root=/dev/VolGroup00/Root
> >          module /initrd-2.6.18-8.1.1.el5xen.img
> >  title CentOS (2.6.18-8.1.1.el5xen) Disk 1
> >          root (hd1,0)
> >          kernel /xen.gz-2.6.18-8.1.1.el5
> >          module /vmlinuz-2.6.18-8.1.1.el5xen ro 
> root=/dev/VolGroup00/Root
> >          module /initrd-2.6.18-8.1.1.el5xen.img
> >  title CentOS (2.6.18-8.1.1.el5xen) Disk 2
> >          root (hd2,0)
> >          kernel /xen.gz-2.6.18-8.1.1.el5
> >          module /vmlinuz-2.6.18-8.1.1.el5xen ro 
> root=/dev/VolGroup00/Root
> >          module /initrd-2.6.18-8.1.1.el5xen.img
> >  title CentOS (2.6.18-8.1.1.el5xen) Disk 3
> >          root (hd3,0)
> >          kernel /xen.gz-2.6.18-8.1.1.el5
> >          module /vmlinuz-2.6.18-8.1.1.el5xen ro 
> root=/dev/VolGroup00/Root
> >          module /initrd-2.6.18-8.1.1.el5xen.img
> >
> > If I had read this thread before I set up this machine I'd have used
> > RAID 6 from the rest of the space, but I used RAID 5 with a 
> hot spare,
> > with LVM on top of that.
> >
> > Before the machine was moved to the colo I tried pulling 
> disks out while
> > it was running and this worked without a problem, which was nice :-)
> >
> > Chris
> >
> >   
> 
> 
> Chris,
> 
> I didn't have to install grub on any of the other volumes, and the 
> server seemed to do well after drive failure (I pulled out 
> drives 1 and 
> 3). 
> In my opinion, neither raid5 or raid6 makes sense with 4 
> drives, as you 
> will get the same amount of space with raid10, but much better 
> performance and availability (although raid6 is supposed to 
> withstand 2 
> drive failures, in my tests it has not done well, and neither has 
> raid5).  As you might've read from the thread, if you want to 
> put the / 
> volume on the raid10, it will not be possible during the install, but 
> you can set up 2 raid1 volumes, and do an LVM stripe across 
> them which 
> should yield comparable performance. 

I think if you setup the 4 disk raid1 at boot grub gets installed
on each as part of the install process.

You'd only need to do it yourself if you put a new disk to replace
a failed one, then just run grub-install on it.

-Ross

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