[parisc-linux] raid-1 on boot disk

[parisc-linux] raid-1 on boot disk

[joel.soete]

Hi all,

I just find a spare disk for my b180 and would like to test md mirroring on my
boot disk.

I am just a bit affraided because Software-RAID-HOWTO mentioned that the
persistent-superblock (requested for boot disk) is writen at the begining of disks.

Is somebody has already test this config and raidtools2 ?

Thanks in advance for info
    Joel


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Re: [parisc-linux] raid-1 on boot disk

[Peter Mottram]

Joel

I did some playing with this some time ago. To have all filesystems under
md control then palo must understand two things:

1. how to read the md filesystem to get the kernel (can use the F0
partition for kernel to get round this)

2. how to use md / filesystem

AFAIK these 2 things just don't work right now & Paul Bame has other more
important things to do with palo right now.

The approach I take is to have a small / and small /boot as normal ext2
partitions & automatically copy these over to spare / & /boot filesystems
on mirror + hot spare disk each night. All other filesystems (including
swap) are on md. If I update the primary boot disk's F0 then I also
update the F0 slice on mirror & spare disks. If the primary boot disk
fails then the system will go down but then can boot off the mirror. Make
sure you set up PRI and ALT boot paths correctly if you want this to
happen automagically & make usre the script which copies / onto the
mirror/spare modifies /etc/fstab appropriately!

R.
PeteM

On Fri, 24 May 2002, joel.soete@freebel.net wrote:

> Hi all,
>
> I just find a spare disk for my b180 and would like to test md mirroring on my
> boot disk.
>
> I am just a bit affraided because Software-RAID-HOWTO mentioned that the
> persistent-superblock (requested for boot disk) is writen at the begining of disks.
>
> Is somebody has already test this config and raidtools2 ?
>
> Thanks in advance for info
>     Joel
>
>
> -------------------------------------------------
> This mail sent through Tiscali Webmail (http://webmail.tiscali.be)
>
> _______________________________________________
> parisc-linux mailing list
> parisc-linux@lists.parisc-linux.org
> http://lists.parisc-linux.org/mailman/listinfo/parisc-linux
>

Re: [parisc-linux] raid-1 on boot disk

[Joel Soete]

Hi Peter,


Peter Mottram wrote:
> Joel
> 
> I did some playing with this some time ago. To have all filesystems under
> md control then palo must understand two things:
> 
> 1. how to read the md filesystem to get the kernel (can use the F0
> partition for kernel to get round this)

I undurstand F0 is a special slice that PDC has to access to load ipl

> 
> 2. how to use md / filesystem
> 

Is a ramdisk (located in the special slice /boot) would not help?
I thought to this because of my read on the use of lvm and evms 
structure system disk. Both write a script to build such ramdisk.

> AFAIK these 2 things just don't work right now & Paul Bame has other more
> important things to do with palo right now.
> 
> The approach I take is to have a small / and small /boot as normal ext2
> partitions & automatically copy these over to spare / & /boot filesystems
> on mirror + hot spare disk each night.

Well ramdisk will avoid to have to do this 'manual' mirror on F0 and 
/boot but there are quasi-static and so easy to mirror with dd. On the 
contrary / is more dynamic so I do not see how do you realise the mirror 
  of this fs?

> All other filesystems (including
> swap) are on md. If I update the primary boot disk's F0 then I also
> update the F0 slice on mirror & spare disks. If the primary boot disk
> fails then the system will go down but then can boot off the mirror. Make
> sure you set up PRI and ALT boot paths correctly if you want this to
> happen automagically & make usre the script which copies / onto the
> mirror/spare modifies /etc/fstab appropriately!
> 
> R.
> PeteM

I am now much more confident, I will try to have a look in more details.

Many thanks for all information,
	Joel