[hobbit] Hobbit cluster and DRDB

[Francesco Duranti]

Hi... 
I use drbd and heartbeat for some clusters at work. We run apache,
mysql, qmail, pound (a free load balancer), an Oracle Instance (where we
cannot use our RAC) and also for the admin server of a weblogic server. 
I'm using drbd 0.7.xx and heartbeat 1.2.x on RHEL3 and RHEL4, 32 and 64
bit. 
Some of those cluster are running from more then one year without any
problems.

Heartbeat it simple to install and need no mainteinance at all, you can
upgrade it without problems (the 2.0 also support multinode cluster).
DRBD can also be configured to get some performance boost at risk for
data writing on disk (he have 3 mode of disk writing). 
If you have a free network card you can dedicate it to heartbeat and
drbd with a crossover cable and at least with Linux the networking work
quite well so you can get good performance on a 1gb network card. 
The only "problem" with drbd is that if you need to upgrade the kernel
you'all also need to recompile the drbd drivers for that kernel or
you'll not see the disks. Heartbeat and drbd will integrate themself
simply without problems. You'll end with a shared disk (that can be only
primary in write access from one node) where you'll install the entire
hobbit home directory, a shared ip address that you will use as ip
address for hobbit.
You will just need one line of configuration in the heartbeat resource
file to put the ip, the device to mount and the script to start hobbit.

Regarding performance I think it will not be so bad but I think it will
depends from how many rrd youre using for graphs. I think that with a gb
network card and a good buffer for io the performance will not be a
problem.

Francesco


> -----Original Message-----
> From: Thomas [mailto:tlp-hobbit at holme-pedersen.dk] 
> Sent: Thursday, August 17, 2006 9:40 PM
> To: hobbit at hswn.dk
> Subject: [hobbit] Hobbit cluster and DRDB
> 
> Hi Brothers,
> 
> Just read an article in Linux Journal about using DRDB as a "cluster" 
> filesystem for a redundant installation of sendmail and 
> mysql. This has caused me to think that this could be a way 
> forward as a cluster mecanism for hobbit. Currently I run a 
> rdist job for this and then have a manual intervention for 
> starting up hobbit on the secondary node.
> 
> I know from when I last looked at DRDB that the IO 
> performance as a problem with BB but with Hobbit I am prety 
> sure it should work.
> 
> I am wondering if any of you have experienced with the 
> DRDB/heartbeat/hobbit and what your impressions are ?
> 
> Regards, Thomas
> 
> 
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