<div><div><div><h2 style="clear: both; font-weight: normal; font-family: arial,helvetica,sans-serif;"><font size="2">Hello, <br></font></h2>I am Praveen, a perl programmer from India.<br><br>Currently I am working on a perl project which requires DRBD . I had gone though the documentation and many other blogs and finally I was able to configure it on my test servers.<br>
<br>Now my client have another requirement, the drbd device on primary should be in read/write mode and the secondary should be in read-only mode.<br><h2 style="clear: both; font-weight: normal; font-family: arial,helvetica,sans-serif;">
<font size="2">I tried to mount the drbd device on the secondary machine in our network and was
unable to do the same as the block device's file system couldn't be
determined on the secondary. Below is the error which came up.<br><br>
# mount /dev/drbd0 /db<br>
mount: block device /dev/drbd0 is write-protected, mounting read-only<br>
mount: Wrong medium type<br><br>
On primary<br><br>
# mount /dev/drbd0 /db<br>
#</font></h2><br>On further researching about drbd, i found the below 2 modes in which drbd could be configured.<br><br><h2 style="clear: both;">Single-primary mode</h2></div></div></div><p>In single-primary mode, any resource is, at any given time,
in the primary role on only one cluster member. Since it is thus
guaranteed that only one cluster node manipulates the data at
any moment, this mode can be used with any conventional file
system (ext3, ext4, XFS etc.).</p><p>Deploying DRBD in single-primary mode is the canonical
approach for high availability (fail-over capable)
clusters.</p><br><div><div><div><h2 style="clear: both;">Dual-primary mode</h2></div></div></div><p>This feature is available in DRBD 8.0 and later.</p><p>In dual-primary mode, any resource is, at any given
time, in the primary role on both cluster nodes. Since
concurrent access to the data is thus possible, this mode
requires the use of a shared cluster file system that utilizes a
distributed lock manager. Examples include
GFS and
OCFS2.</p><p>Deploying DRBD in dual-primary mode is the preferred
approach for load-balancing clusters which require concurrent
data access from two nodes. This mode is disabled by default,
and must be enabled explicitly in DRBD's configuration
file.<font color="#888888"><br></font></p><p><br></p><p>I had communicated this finding with my client, but the client want this to be done in Single-primary mode. Could anyone guide me on how this could be accomplished.</p>
<p></p><p>Also I have another doubt. I have servers a, b, c and d. Can I club LVM devices on all 4 server to make a drbd resource ? I don't have the resource to test this practically. This is another advanced required of the client, which needs to be implemented after the first module is completed. If it is possible do I simply add the the servers to the resource and one server will act as primary and all others as secondary ? <br>
<font color="#888888"></font></p>Waiting for the valuable guidance.<br clear="all"><br>-- <br>#####################<br># Praveen~ #<br># +919895066033 #<br>#####################<br>