Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi,
I am using DRBD version 8.4 on CentOS6 and having some issues in
understanding the replication mechanism.
Configuration Details:
---------------------------------
[root at centos6 ~]# drbdadm --version
DRBDADM_API_VERSION=1
DRBD_KERNEL_VERSION_CODE=0x080407
DRBDADM_VERSION_CODE=0x080905
DRBDADM_VERSION=8.9.5
[root at centos6 ~]# rpm -qa | grep drbd
drbd84-utils-8.9.5-1.el6.elrepo.x86_64
kmod-drbd84-8.4.7-1_1.el6.elrepo.x86_64
DRBD Configuration on both Primary and Secondary nodes:
-----------------------------------------------------------------------------------------
resource r0
{
on centos6
{
device /dev/drbd1;
disk /dev/sdb;
address 10.168.150.2:7789;
meta-disk internal;
}
on vm-centos6-dev1
{
device /dev/drbd1;
disk /dev/vdb;
address 10.168.3.28:7789;
meta-disk internal;
}
}
Setup on Primary:
---------------------------
1) Created a primary node (VM) [10.168.150.2 (centos6)] with secondary hard
disk /dev/sdb. This disk was filtered in LVM conf.
2a) pvcreate /dev/drbd1
2b) vgcreate VolGroup_DRBD /dev/drbd1
2c) lvcreate --size 20G --name LV_DRBD VolGroup_DRBD
3a) drbdadm create-md r0
3b) drbdadm up r0
3c) drbdadm primary --force r0
4) mkfs.ext3 /dev/drbd1
5) mkdir /db/pgdata
6) mount -t ext3 /dev/drbd1 /db/pgdata
7) cp /root/conf1.xml /db/pgdata/conf1.xml
Setup on Secondary:
---------------------------------
1) Created a secondary node (VM) [10.168.3.28 (vm-centos6-dev1)] with
secondary hard disk /dev/vdb. This disk was filtered in LVM conf.
2a) pvcreate /dev/drbd1
2b) vgcreate VolGroup_DRBD /dev/drbd1
2c) lvcreate --size 20G --name LV_DRBD VolGroup_DRBD
3a) drbdadm create-md r0
3b) drbdadm up r0
4) mkfs.ext3 /dev/drbd1
5) mkdir /db/pgdata
Tests and Result:
-------------------------------------
1) To see that file created in step #7 on primary was replicated in
secondary I manually umount partition on primary and demoted the current
primary to secondary:
1a) umount /db/pgdata
1a)drbdadm secondary r0
2) On secondary I manually mounted the partition (mount -t ext3 /dev/drbd1
/db/pgdata) and promoted it to primary (drbdadm primary --force r0)
3) Now I could see file created in step #7 is replicated on secondary as
well.
Problem:
----------------
1) How to check that file created on primary was replicated in secondary
without demoting primary and promoting secondary?
2a) How to replicate files on an already mounted filesystem? Example how to
replicate /etc/mydir/myconf.xml or /usr/lib/mydir/mydata which are already
mounted on / (root) partition. In my setup this
cannot be made DRBD partition.
2b) I tried soft link route (ln -s /etc/mydir/myconf.xml
/db/pgdata/myconf.xml) but changes made on primary /etc/mydir/myconf.xml
were not replicated on secondary /etc/mydir/myconf.xml
via the soft link?
2c) How this can be done?
--Raman
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