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Re: Debian+LVM+RAID

On Thu, Jul 09, 2009 at 10:34:13AM +0700, Vilasith Phonepadith wrote:

> Problem: I have to install Debian with the requirements as
> follow:partition: use the system of LVM for partitionning the
> serversif possible on the Disk RAID1 Mirroring I don't understand
> well and don't know how to start. Which one should be done first,
> after or at the same time.

Why do you need LVM?

Imho it is better to create a partitionable RAID array first and then
to create the partitions you want to have on the partitionable RAID

The RAID array must be partitionable, which is an option you
eventually need to specify when creating it. I don't know what the
options the installer offers are doing by default, but I would think
that you should be able to open the shell and create the RAID array
with mdadm manually. Once you have the partitionable RAID array, you
should be able to partition it from within the installer like any
other disk.

To clarify: There are partitionable RAID arrays and non-partitionable
RAID arrays. When creating a RAID array, you need to specify which
kind --- partitionable or non-partitionable --- you want to create.

If you want to use non-partitionable RAID arrays, you would create
identical partitions on all of the disks involved and then use those
partitions to create the RAID arrays. Another poster already described
that better.

If you want to use a partitionable RAID array, you can use whole disks
(without partitioning the disks) to create the RAID array. Then you
can partition the RAID array.

As to LVM, I can't say much since I haven't used it yet. And without
knowing more about what you are trying to achieve and why you might
need LVM, there's not much advice that could be given.

If you can avoid using LVM, don't use it. It's always better to keep
things simple. If you want to use LVM because you might want to add
more disks later to make the partitions larger, it would make sense to
me to first create a partitionable RAID array and then to create LVM
partitions as needed on the RAID array. When you're adding more disks
later, you would again create a partitionable RAID array from the
additional disks and use the array with LVM.

But there are other possible uses of LVM which may suggest a different
approach ...

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