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From: Michael Prokop <mika <at> grml.org>
Subject: Re: [Grml-devel] Request for contribution: SW-RAID
Newsgroups: gmane.linux.distributions.grml.user
Date: Saturday 18th February 2006 23:53:27 UTC (over 11 years ago)

Thanks to the ones who contributed. Finally we have a solution which
should be acceptable.

* Michael Prokop  [20060217 14:45]:

> We are working on improving software (SW) RAID support within grml
> and would appreciate your help and opion about it. Please contribute!

> As you maybe know, partitions of type 0xfd (Linux raid autodetect)
> are scanned and automatically assembled into RAID arrays by the
> kernel.  We noticed a strange behaviour on automatic assembling
> (nothing serious but a little bit confusing) and try to figure out
> what's the reason for it.

Linux raid autodetect devices (0xfd) are assembled by default on
grml.  That's working currently and as long as upstream does not
remove this features (see linux.raid mailinglist for details) we
will support it as well.

> * If you boot grml on a box using SW-RAID: do you expect to get a
>   running SW-RAID setup (using the /dev/md? devices) or do you
>   prefer to set it up and start on your own (so neither grml nor
>   kernel touches it)?

Automatic assembling of md works if kernel supports the device(s)
and because md is compiled statically into our kernel.

Accesssing devices works on P-ATA devices, but not on (all) S-ATA
and SCSI devices as all the S-ATA/SCSI modules would have to be part
of the kernel (statically compiled).

So if you have a md running on S-ATA/SCSI which is not started by
default just run 'mdrun' after booting grml. Take a look at 'cat
/proc/mdstat' to check which and whether devices are up and running.

If you absolutely do not want to use the automatic assembling of
SW-RAID use the kernel commandline 'raid=noautodetect'. So boot your
grml system via 'grml raid=noautodetect'. This has been added to the
forensic cheatcode as well (for next versions of grml).

> * Say you have /dev/hda1 and /dev/hdb1 as part of SW-RAID /dev/md0.
>   Do you expect to get entries for /dev/hda1, /dev/hdb1 and /dev/md0
>   in your /etc/fstab? Which entries do you expect to get?

You will get entries for "/dev/md?" coresponding to the filesystem
type on the device. It is not mounted by default and mounting is
restricted to user root.

You will also get entries named "/dev/hd?" with filesystem type
linux_raid_member if the device is part of a linux raid. As for
"/dev/md?" they are not mounted by default, mounting is restricted
to user root and mounting won't work for security reasons due to
filesystem linux_raid_member.


The above information will apply for grml releases starting with the
upcoming development release grml 0.6-2. If you notice anything
which does not behave as documented feel free to submit a bug
report to me. Thank you.

HTH, JFYI && regards,
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