Re: [gentoo-user] Re: initramfs & RAID at boot time

[Mark Knecht <markknecht@gmail.com>]

On Sun, Apr 18, 2010 at 11:01 AM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Sun, 18 Apr 2010 08:13:08 -0700, Mark Knecht wrote:
>
>> I'm not sure that we good advice or not for RAIDs that could be
>> assembled later but that's what I did and it leads to the kernel
>> trying to do everything before the system is totally up and mdadm is
>> really running.
>
> I only have one RAID1 of 400MB for / and one RAID5 carrying an LVM volume
> group for everything else. Using multiple RAID partitions without LVM is
> far to complicated for my brain to handle.
>
>
> --
> Neil Bothwick

Nahh...I don't believe that for a moment, but this is a rather more
complicated task than a basic desktop PC. This is about number
crunching using multiple instances of Windows running under VMWare.

First, the basic system:

/dev/md3 - 50GB 3-drive RAID1 => The ~amd64 install we discussed over
the last week. This is the whole Gentoo install.
/dev/md5 - 50GB 3-drive RAID1 => A standard stable install - same as
md3 but stable, and again the whole Gentoo install.

Obviously I don't use the two above at the same time. I'm mostly on
stable and testing out ~amd64 right now. I use one or the other.

/dev/md11 => 100GB RAID0 - This partition is the main data storage for
the 5 Windows VMs I want to run at the same time. I went RAID0 because
my Windows apps appear to need an aggregate disk bandwidth of about
150-200MB/Sec and I couldn't get that with RAID1. I'll see how well
this works out over time.

/dev/md6 => 250GB RAID1 used purely as backup for the RAID0 which is
backed up daily, although right now not automatically.

The RAID0 and backup RAID1 need to be available whether I'm booting
stable (md5) or ~amd64. (md3)

I found some BIOS options, one of which was as default set to 'Fast
Boot'. I disabled that, slowing down boot and hopefully allowing far
more time to get the drives online more reliably. So far I've powered
off and rebooted 5 or 6 times. Each time the system has come up clean.
That's a first.

I could maybe post a photo of what I'm seeing at boot but essentially
the boot process complains with red exclamation marks about md6 & md11
but in dmesg the only thing I find is the one-liner

md: created md3
md: bind<sda3>
md: bind<sdc3>
md: bind<sdb3>
md: running: <sdb3><sdc3><sda3>
raid1: raid set md3 active with 3 out of 3 mirrors
md3: detected capacity change from 0 to 53694562304
md: ... autorun DONE.
md5: unknown partition table

and after that no other messages.

BTW - I did sort of take a gamble and change the partitions for md6
and md11 to type 83 instead of 0xfd. It doesn't appear to have caused
any problems and I have only the above 'unknown partition table'
message. Strange as md5 is mounted and the system seems completely
happy:

mark@c2stable ~ $ df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/md5              51612920   7552836  41438284  16% /
udev                     10240       296      9944   3% /dev
/dev/md11            103224600  17422220  80558784  18% /virdata
/dev/md6             243534244  24664820 206498580  11% /backups
shm                    6151580         0   6151580   0% /dev/shm
mark@c2stable ~ $

Cheers,
Mark