[DRBD-user] Help: lower Device Already Claimed

day knight back2games at gmail.com
Thu May 26 02:03:45 CEST 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hello all,

I have searched on google and found out that lower device should not be
mounted which has lead to a lot of confusion. My problem is, I am trying to
configure /dev/sda to work with DRBD hence the error "Lower Device Already
Claimed". It works well when I use /dev/sdb or unmounted partition. As we
all know that in runlevel 3, the / (slash root) cannot be unmounted as it is
being used so the question becomes how would I make DRBD work with /dev/sda
on which I have / (slash root) mounted.

*What I am trying to do.*
I want to mirror one drive over the network with another drive to serve for
failover purposes (I believe as DRBD states it is like a RAID1 over the
network). the two systems master and slave would run exact configuration
both hardware and software.

therefore for test purposes, I have created /dev/sda1 on which / (slash
root) resides. This / contains the base structure created by Centos such as

/
/boot
/dev
/bin
/home
/etc

I also have free space that can be partitioned to create /dev/sda2.

Now all programs such as httpd, mysql, vsftpd, webmin, bind, sendmail,
dovecot and many others are installed with in the /dev/sda1 as well as the
data associated with these programs also resides on the /dev/sda1

*What I don't understand*

If I use /dev/sda2 which is unmounted partion then what would I need to do
in terms of setup to ensure that the entire /dev/sda is replicated or how
would I mount the /dev/drbd0 to /

Confusing :D

Thank you all and I am looking forward to your expert responses, leads,
assistance :)

Sincerely
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