[gentoo-user] [OT] Moving system from "single-disk" to RAID-1 configuration

[gentoo-user] [OT] Moving system from "single-disk" to RAID-1 configuration

[Dan Johansson]

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Hi,

I have a setup Gentoo on a Box with a onboard ATA Raid controller (Promise 
PDC20265 FastTrak100 Lite/Ultra100). At the moment I am only using one 
ATA-Disk on this controller (this is the only disk in the system).
Now I want to add a second Disk to this system and setup a RAID-1 
configuration. Can someone point me to a good HOWTO or something similar 
which describes how to setup this (grub/lilo/dm/...) on a 2.6 kernel.

Regards,
-- 
Dan Johansson, <http://www.dmj.nu>
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[gentoo-user] Re: [OT] Moving system from "single-disk" to RAID-1 configuration

[Francesco Talamona]

On Sunday 23 October 2005 15:53, Dan Johansson wrote:
> Hi,
>
> I have a setup Gentoo on a Box with a onboard ATA Raid controller
> (Promise PDC20265 FastTrak100 Lite/Ultra100). At the moment I am only
> using one ATA-Disk on this controller (this is the only disk in the
> system). Now I want to add a second Disk to this system and setup a
> RAID-1 configuration. Can someone point me to a good HOWTO or
> something similar which describes how to setup this
> (grub/lilo/dm/...) on a 2.6 kernel.
>
> Regards,

Many howtos mix raidtools and mdadm, this one [1] IMO is much clear.

At the moment I'm running a system with a RAID1 for /boot and another 
RAID1 for root, and a LVM2 on top of a RAID5 for everything else. [3]

The most difficult thing was making disc naming sticky, I have a ASUS 
A8V with a Via and a Promise controller, and the disk naming was so 
sloppy that if sda failed all other disks were renamed to accommodate 
in the free namespace, not at all reliable!
See [2]. 

In the end, after udev fine tuning, I managed to build a degraded array 
of 4 disks using 3 discs (the RAID1 for /boot was built with 3 of 3 
from the start) using instruction and suggestion in [1], no need 
for /etc/raidtab!

A livecd that recognizes your hardware and has mdadm, lvm... is an 
invaluable rescue tool, test it before all.

[1]http://www.linuxdevcenter.com/pub/a/linux/2002/12/05/RAID.html
[2]http://forum.hardware.fr/hardwarefr/OSAlternatifs/RAID-Soft-SATA-SCSI-Les-disques-changent-resolu-sujet-51807-1.htm
[3]http://www.gentoo.org/doc/en/lvm2.xml

ciao
	Francesco
-- 
Linux Version 2.6.12-gentoo-r9, Compiled #2 Wed Aug 24 18:43:16 CEST 
2005
One 2.2GHz AMD Athlon 64 Processor, 2GB RAM, 4325.37 Bogomips Total
aemaeth
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Re: [gentoo-user] Re: [OT] Moving system from "single-disk" to RAID-1 configuration

[Mike Williams]

On Monday 24 October 2005 19:28, Francesco Talamona wrote:
> The most difficult thing was making disc naming sticky, I have a ASUS
> A8V with a Via and a Promise controller, and the disk naming was so
> sloppy that if sda failed all other disks were renamed to accommodate
> in the free namespace, not at all reliable!

I don't read french, so I don't know what that URL said, but device naming is 
not an issue.
All you need to do is change the partition type to fd "Linux raid autodetect", 
then either:
1) Compile all the raid/ide/scsi drivers you need into the kernel, and all 
your arrays will be automagically created on startup.
2) Add an entry like at the bottom of page 1 of the linuxdevcenter article, 
except all you actually need is this:

DEVICE partitions
ARRAY /dev/md0 uuid=8ef83d67:79b230ba:6cc967c3:208b9224

I have a SATA card that doesn't have in kernel drivers, so I have to load a 
module, which naturally means the kernel can't autostart all my arrays, but 
mdadm can without me having to tell it any device nodes.

-- 
Mike Williams
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[gentoo-user] Re: [OT] Moving system from "single-disk" to RAID-1 configuration

[Francesco Talamona]

On Monday 24 October 2005 22:02, Mike Williams wrote:
> On Monday 24 October 2005 19:28, Francesco Talamona wrote:
> > The most difficult thing was making disc naming sticky, I have a
> > ASUS A8V with a Via and a Promise controller, and the disk naming
> > was so sloppy that if sda failed all other disks were renamed to
> > accommodate in the free namespace, not at all reliable!
>
> I don't read french, so I don't know what that URL said, but device
> naming is not an issue.
I made an exstensive serie of test before running into troubles... It 
was an occasion to understand udev in depth.

> All you need to do is change the partition type to fd "Linux raid
> autodetect", then either:
> 1) Compile all the raid/ide/scsi drivers you need into the kernel,
> and all your arrays will be automagically created on startup.
> 2) Add an entry like at the bottom of page 1 of the linuxdevcenter
> article, except all you actually need is this:
>
> DEVICE partitions
> ARRAY /dev/md0 uuid=8ef83d67:79b230ba:6cc967c3:208b9224
AFAIK fd partition type is mandatory. Anyway is good to know that I can 
avoid explicit node names in config files.

> I have a SATA card that doesn't have in kernel drivers, so I have to
> load a module, which naturally means the kernel can't autostart all
> my arrays, but mdadm can without me having to tell it any device
> nodes.
How can you prevent it to start in degraded mode?

ciao
	Francesco
-- 
Linux Version 2.6.12-gentoo-r9, Compiled #2 Wed Aug 24 18:43:16 CEST 
2005
One 2.2GHz AMD Athlon 64 Processor, 2GB RAM, 4325.37 Bogomips Total
aemaeth
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Re: [gentoo-user] Re: [OT] Moving system from "single-disk" to RAID-1 configuration

[Mike Williams]

On Tuesday 25 October 2005 06:01, Francesco Talamona wrote:
> > DEVICE partitions
> > ARRAY /dev/md0 uuid=8ef83d67:79b230ba:6cc967c3:208b9224
>
> AFAIK fd partition type is mandatory. Anyway is good to know that I can
> avoid explicit node names in config files.

I'm not sure it's mandatory, but there really is no reason not to do so.

> > I have a SATA card that doesn't have in kernel drivers, so I have to
> > load a module, which naturally means the kernel can't autostart all
> > my arrays, but mdadm can without me having to tell it any device
> > nodes.
>
> How can you prevent it to start in degraded mode?

I don't have the raid drivers compiled into the kernel :)
I have 3 arrays, 2 of which have more devices on the SATA card than the array 
can loose. mdadm would warn me by email if it detected any array in degraded 
mode anyway.

I'm not sure what problem you had that meant you could only create a degraded 
array. But if you boot from a gentoo livecd you can create a mirror from an 
existing disk *without* losing any data, or needing to backup. If you specify 
the disk/partition with the data on it you want to keep *first* to mdadm, 
that data will get replicated to the others.

-- 
Mike Williams
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Re: [gentoo-user] Re: [OT] Moving system from "single-disk" to RAID-1 configuration

[Dan Johansson]

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On Tuesday 25 October 2005 12.27, Mike Williams wrote:
> On Tuesday 25 October 2005 06:01, Francesco Talamona wrote:
> > > DEVICE partitions
> > > ARRAY /dev/md0 uuid=8ef83d67:79b230ba:6cc967c3:208b9224
> >
> > AFAIK fd partition type is mandatory. Anyway is good to know that I can
> > avoid explicit node names in config files.
>
> I'm not sure it's mandatory, but there really is no reason not to do so.
>
> > > I have a SATA card that doesn't have in kernel drivers, so I have to
> > > load a module, which naturally means the kernel can't autostart all
> > > my arrays, but mdadm can without me having to tell it any device
> > > nodes.
> >
> > How can you prevent it to start in degraded mode?
>
> I don't have the raid drivers compiled into the kernel :)
> I have 3 arrays, 2 of which have more devices on the SATA card than the
> array can loose. mdadm would warn me by email if it detected any array in
> degraded mode anyway.
>
> I'm not sure what problem you had that meant you could only create a
> degraded array. But if you boot from a gentoo livecd you can create a
> mirror from an existing disk *without* losing any data, or needing to
> backup. If you specify the disk/partition with the data on it you want to
> keep *first* to mdadm, that data will get replicated to the others.

Thanks for your input. Just one Question about setting the partition type to 
'FD' - should I do this for all Partitions or ?
Today I have the following Partitions defined
Partition	Type	FS
/dev/hde1	83	/boot
/dev/hde2	82	(SWAP)
/dev/hde3	83	/
/dev/hde4	8E	(LVM)

Regards,
-- 
Dan Johansson, <http://www.dmj.nu>
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Re: [gentoo-user] Re: [OT] Moving system from "single-disk" to RAID-1 configuration

[Mike Williams]

On Tuesday 25 October 2005 18:02, Dan Johansson wrote:
> Thanks for your input. Just one Question about setting the partition type
> to 'FD' - should I do this for all Partitions or ?

Which ever partitions you are going to create raid arrays from, but I don't 
imagine it would do any real harm to those that aren't going to be part of an 
array.

-- 
Mike Williams
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