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SubjectRe: Linux mdadm superblock question.
Henrique de Moraes Holschuh wrote:
> On Sat, 13 Feb 2010, Michael Evans wrote:
>
>> I remember hearing that 1.x had /no/ plans for kernel level
>> auto-detection ever. That can be accomplished in early-userspace
>> leaving the code in the kernel much less complex, and therefore far
>> more reliable.
>>
>
> Yes, it is far more reliable kernel side, if only because it doesn't do
> anything.
>
> But the userspace reliability is _not_ good. initrds are a source of
> problems the moment things start to go wrong, and that's when they are not
> the problem themselves.
>
> And the end result is a system that needs manual intervention to get its
> root filesystem back.
>
> In my experience, every time we moved critical codepaths to userspace, we
> ended up decreasing the *overall* system reliability.
>
I don't see it like this.
You have the same chance to screw up the system by making mistakes in
the files in /etc, in the networking config, the firewall, the server
applications...
(note: I speak for Debian/Ubuntu, redhat's initramfs I think is more messy.)
1.x autodetection worked great for me in initramfs. Basically you only
need /etc/mdadm/mdadm.conf copied to initramfs (via update-initramfs),
the rest is done by Debian/Ubuntu standard initramfs procedure.
Also consider 1.x allows to choose which arrays are autoassembled
(hostname written in the array name equal to hostname in the machine or
specified in mdadm.conf): this is more precise than 0.9 which
autoassembles all, I think.


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