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Re: LVM + dmraid

David Abrahams wrote:

The first piece is that I've now dropped dmraid for mdraid, since I
don't *really* need to dual boot to Windows.  I want to run Windows
virtualized.  Is anyone going to argue that I'm giving up something
important by using mdraid?

The key issues for me are the ability to dual boot with windows, and to boot from a raid0 ( stripe ). With mdraid you can only boot from a normal partition or a raid-1, and if the primary disk fails, the system will not boot until you manually remove the failed disk or direct the bios to boot from the other disk instead ( you DID manually copy the boot partition to the second disk right? ).

What kind of logical volumes did you create within the volume group?

Typical/aggressive arrangement:

/ 100M
/usr 50G
/var (also storing /tmp here) 10G
/var/spool 4G
/var/log 4G
/home 200G
/swap 16G
/usr/local 50G

Ok, what is the device name that corresponds to /? It needs to be passed to the kernel in the root= parameter.

/boot is on a primary partition outside LVM

How did you direct the system to boot from the correct root volume (
root= kernel parameter )?

The FakeRaidHowo tells all.  I really did follow the directions :)

It does not describe the specific parameters that YOU used. The examples given in the howto only apply to the specific partition layout that I had, you are supposed to modify it to match your layout, not copy verbatim.

I have not used LVM before but I have read a good deal about it, but I
wrote the FakeRaidHowto you followed so I may be able to help.

Oh!  I've spent many hours with your webpage, so thanks (I think ;->)
for writing it!

You're welcome.

Well, IIRC there was nothing useful mounted on /root.  I don't
remember exactly what it was, but it just contained lost+found.  I can
mount /boot on /root and I see the files.

Which is why it sounds like you are mounting the wrong root filesystem. If you were mounting the root filesystem it should contain at least direcories for /dev, /sys and /proc. Since this filesystem is empty ( save for lost+found ) it must be one of the other filesystems you created ( maybe /var? ).

LVM has lots of benefits in terms of flexibility.  It's easy to
non-destructively resize partitions, including extending them into new
disks when you run out of space.  There's snapshotting and many other
useful (-sounding) features.  I'm not an expert sysadmin yet, but I
don't want to cut myself from these capabilities at step 1.

It does appear to be handy in terms of ease of use, but resizing partitions and snapshotting can be done without LVM if you wish. I chose not to use it mainly so that I can boot directly from the raid ( no non raided boot partition needed ) and dual boot with windows ( it doesn't understand LVM ).

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