Hello everyone,
I am running a Redhat9 with a 36gb scsi HD and I need to install a
mirror HD on it (raid1). I think raidtools will work for me, but I
have a question in how to setup it up.

I Already purchased a identical HD and physically installed it. Also,
I already install the raidtools software on my machine.

In all "how-to" I have seen so far, they only show how to setup
raidtools with new hard drives (which are not in production and with
any data).

What I need to know is: How to add the mirror drive in a HD already in
production and with critical data?


My hardrive with the data and OS is

[root@localhost root]# df
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 33G 21G 11G 66% /
/dev/sda1 99M 15M 80M 16% /boot
none 251M 0 251M 0% /dev/shm

The mirror hardrive is

[root@localhost root]# df /dev/sdb
Filesystem Size Used Avail Use% Mounted on
/dev/sdb 33G 21G 11G 66%


Base in what I read, that's how my raidtools looks like
/etc/raidtab
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
nr-spare-disks 0
chunk-size 4
persistent-superblock 1
device /dev/sda1
raid-disk 0
device /dev/sdb1
raid-disk 1

Is it correct ?

If so, when I try to start the raid, I have this message:


[root@localhost /]# mkraid /dev/md0
handling MD device /dev/md0
analyzing super-block
disk 0: /dev/sda1, 104391kB, raid superblock at 104320kB
/dev/sda1 is mounted
mkraid: aborted.
(In addition to the above messages, see the syslog and /proc/mdstat as
well
for potential clues.)

I claims my HD is mounted, But how Can I umount my main hardrive, if
the system is on it?



Thanks for any help you guys can provide.
Alvaro Melo

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Alvaro Melo <alvaro_melo@yahoo.com> wrote:
> Hello everyone,
> I am running a Redhat9 with a 36gb scsi HD and I need to install a
> mirror HD on it (raid1). I think raidtools will work for me, but I
> have a question in how to setup it up.

> I Already purchased a identical HD and physically installed it. Also,
> I already install the raidtools software on my machine.

> In all "how-to" I have seen so far, they only show how to setup
> raidtools with new hard drives (which are not in production and with
> any data).

[..]

> I claims my HD is mounted, But how Can I umount my main hardrive, if
> the system is on it?

You need one disk more, setup/initialize the raid set, copy your
system over, edit fstab and rerun lilo, it would be a good idea to
do this from single user mode, or even from a rescue system,
depending on what there's running on the system.

AFAIR you can't setup sw raid without loosing all data on your
disks.

Good luck

--
Michael Heiming (GPG-Key ID: 0xEDD27B94)

Remove +SIGNS and www. if you expect an answer, sorry for
inconvenience, but I get tons of spam.
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alvaro_melo@yahoo.com (Alvaro Melo) writes:

>Hello everyone,
>I am running a Redhat9 with a 36gb scsi HD and I need to install a
>mirror HD on it (raid1). I think raidtools will work for me, but I
>have a question in how to setup it up.

>I Already purchased a identical HD and physically installed it. Also,
>I already install the raidtools software on my machine.

>In all "how-to" I have seen so far, they only show how to setup
>raidtools with new hard drives (which are not in production and with
>any data).

No. Please read the Software-RAID-HOWTO; it specifically explains
how to setup a SW-RAID on an already existing filesystem.

>What I need to know is: How to add the mirror drive in a HD already in
>production and with critical data?

[...]

By marking the _existing_ disk in /etc/raidtab as failed, copying the
contents over onto the newly installed RAID that will then be running
in degraded mode (at that time), and re-adding the old disk using
raidhotadd.

WARNING: Don't try that without having a backup ready. If you mess
things up, all existing data will be lost.

Sidenote: I wouldn't bother booting off of the RAID; instead, keep
the / and /boot filesystem on separate partitions, and run rsync
on a regular base.

Michael