On 8/7/07, Neil Brown <[EMAIL PROTECTED]> wrote:
> On Tuesday August 7, [EMAIL PROTECTED] wrote:
> > On 8/7/07, Neil Brown <[EMAIL PROTECTED]> wrote:
> > > On Tuesday August 7, [EMAIL PROTECTED] wrote:
> > > > how can I create raid 5 array that preserves the contents of a given
> > > > disk (part of the array)?
> > > > I can do that in two steps, raid 5 on two disks then reshape it to be
> > > > real raid5, but is there a direct way to do it?
> > >
> > > What do you mean by "real raid 5". Two disks are just as much an
> > > array as 10.
> > I meant by real raid 5 to raid 5 over 3 drives or above.
> > > What do you mean by "direct". If I understand your requirements
> > in one mdadm command
> > > correctly, there are two obvious steps.
> > > 1/ make the data appear in a raid5
> > > 2/ change the number of devices in the raid5.
> > >
> > > Are two steps too many?
> > in this case I two options:
> > 1. keep the filesystem unmounted tell step 1 in done -> the fs will
> > not be available for long time
>
> No, it shouldn't take a long time....
>
> What exactly do you have, and what exactly do you want to achieve?
>
> If think you started of by saying you wanted to convert a raid1 to a
> raid5. Yes, that requires the filesystem to be unmounted, but only
> takes seconds to achieve:
>
> mdadm -S /dev/md0
> mdadm -C /dev/md0 -l5 -n2 /dev/sda1 /dev/sdb1
> mount /dev/md0
>
> If you have a single-disk, you first might need to shrink the
> filesystem to make sure there is 128K free at the end of the device:
>
> umount /filesystem
> resize2fs /dev/sda1 whatever-number
> mdadm -C /dev/md0 -l5 -n1 /dev/sda1 missing
-n1 didn't work, but -n2 succeeded.
> mount /dev/md0 /filesystem
> # now add the drives and grow
> mdadm /dev/md0 --add /dev/sdb1 /dev/sdc1
> # wait for recovery to finish
> mdadm --grow /dev/md0 --raid-disks=3
>
> something like that..
great, this actually does the migration from single drive to raid5 as
I was looking for.
thanks.
>
> NeilBrown
>
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