Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Wednesday 08 October 2008 21:33:24 kevin kempter wrote:
> Hi List;
>
> I'm a newbie to DRBD and I've hit a snag.
>
> Here's what I've done:
>
> 1) I setup 2 new installs of CentOS v5 (32bit) as VM's via vmware
> server on a Dell 2900 (quad core, 16Gram, single RAID slice, etc)
What I describe below is on CentOS 5.2, using the DRBD 8.0.13 packages from
the CentOS Extras repository.
> Note: I created /stage as a separate ext2 filesystem (mounted from /
> dev/sda2). This is the filesystem I want to replicate with drbd
There should be no filesystem on the raw partition(s) you want to replicate.
I'd unmount the partition(s) and erase the first few meg to be sure DRBD
thinks they're blank ("dd if=/dev/zero of=/dev/whatever bs=10M count=1"
should do it)
>
> 2) downloaded and compiled the drbd source (v 8.2.6) on both servers
As an aside, DRBD 8.2.x is available via CentOS Extras, assuming you're using
the CenOS Plus kernel.
DRBD 8.0.x is available for the default CentOS kernel from CentOS Extras.
> 4) edited my /etc/drbd.conf on both servers (VM's) to look like this:
<snip>
> resource r0 {
>
> on CentOS-32-VM1 {
> device /dev/drbd1;
Traditionally you'd start with /dev/drbd0...
> disk /dev/sda2;
> address 192.168.1.50:7788;
> meta-disk internal;
> }
>
> on CentOS-32-VM2 {
> device /dev/drbd1;
> disk /dev/sda2;
> address 192.168.1.51:7788;
> meta-disk internal;
> }
> }
>
Missing step: initialise the resource:
On both nodes, "drbdadm create-md r0"
> 5) Installed the drbd module
On both nodes, "service drbd start" will do this too.
(See: http://www.drbd.org/docs/install/ )
> 6) attempted to run drbdadm attach
This is moot if you start the service instead.
/proc/drbd on both nodes will show something like:
version: 8.0.13 (api:86/proto:86)
GIT-hash: ee3ad77563d2e87171a3da17cc002ddfd1677dbe build by
buildsvn at c5-i386-build, 2008-08-07 13:40:24
0: cs:Connected st:Secondary/Secondary ds:Inconsistent/Inconsistent C r---
ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
resync: used:0/61 hits:0 misses:0 starving:0 dirty:0 changed:0
act_log: used:0/257 hits:0 misses:0 starving:0 dirty:0 changed:0
At this point you need to tell DRBD which node is Primary. On your prefered
primary node:
drbdadm -- --overwrite-data-of-peer primary r0
/proc/drbd will now change to (during the sync it will show sync progress):
GIT-hash: ee3ad77563d2e87171a3da17cc002ddfd1677dbe build by
buildsvn at c5-i386-build, 2008-08-07 13:40:24
0: cs:Connected st:Primary/Secondary ds:UpToDate/UpToDate C r---
ns:200736 nr:0 dw:0 dr:200736 al:0 bm:13 lo:0 pe:0 ua:0 ap:0
resync: used:0/61 hits:12533 misses:13 starving:0 dirty:0 changed:13
act_log: used:0/257 hits:0 misses:0 starving:0 dirty:0 changed:0
Now you can create a filesystem:
mke2fs -j /dev/drbd0
Then mount it by hand to check:
mkdir /mnt/drbd_r0
mount /dev/drbd0 /mnt/drbd_r0
Once you're happy this works, you'll want to use something like heartbeat to
deal with migrating/mounting the resource in the event of a failure. The DRBD
init script will put you into the Secondary/Secondary state; heartbeat will
control promoting to Primary and mounting:
/etc/ha.d/haresources:
node1.example.com drbddisk::r0 Filesystem::/dev/drbd0::/mnt/drbd_r0::ext3
Regards,
Mark.
--
Mark Watts BSc RHCE MBCS
Senior Systems Engineer
QinetiQ Applied Technologies
GPG Key: http://www.linux-corner.info/mwatts.gpg
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