[DRBD-user] Newbie confusion

Etienne van Tonder evt at infoware.com.au
Fri Oct 7 13:27:09 CEST 2005

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


Hi Phil,

Thank you for the reply it helped clear up a few things for me and I have
now got everything configured and working.

Couple of other questions for which I could not find a definitive answer:

1. How do I start drbd/heartbeat at boot time. I'm using Suse 9.3Pro, what
would be the best method for loading these in such a way as to make sure
drbd is finished loading before HB starts or is that not important. Should I
simply do a chkconfig drbd 35, chkconfig heartbeat 35 as I read somewhere or
add it to the modprobe.conf.local file?? Once drbd is loaded then I think HB
should be able to do the rest, but I want to make sure drbd is loaded before
this happens..

2. Do I need to do anything at shutdown or will HB handle this for me,
should I be running some sort of shutdown script?

3. What should I normally expect to happen if I shutdown both machines and
only bring back the primary, will it run in standalone mode allowing me
access to the shared data. Once it detects the secondary will it then
connect and sync? What would happen if I did the reverse?

Regards,

Etienne.

----- Original Message -----
From: "Philipp Reisner" <philipp.reisner at linbit.com>
To: <drbd-user at lists.linbit.com>
Sent: Wednesday, October 05, 2005 11:43 PM
Subject: Re: [DRBD-user] Newbie confusion


Am Mittwoch, 5. Oktober 2005 11:51 schrieb Etienne van Tonder:
> I've spent most of today reading the archives and many articles on DRBD, I
> have a few questions if I may. I have an existing system running Suse9 pro
> with RAID1, I've bought an exact same server and would like to set them up
> running hearbeat and DRBD.
>
> 1. I presume I have to setup DRBD first and then Heartbeat.
>
Right.

> 2. I'm a bit confused, when I think of RAID1 I think of a complete disk
> being mirrored. Is this not the case with DRBD? From what I have read it
> seems like it really only mirrors a single partition, is this correct? If
> so what about the system files, if I make a change to a config file on the
> primary, this change will not be mirrored to the secondary automatically?

You should only mirror the "data" partition, you can not mirror the
root FS with plain DRBD. (The other thing would be openSSI's DRBD, but that
is
way out of the context here.)
It a kind of chicken - egg problem.

>
> 4. If I can not mirror the complete disk, what do I do with the data that
> I'd like to mirror that currently exists on sda3. In particular I have a
> posgresql database, php files that I change from time to time, and any
> other files that I need to mirror. Do I have to copy these files to the
> DRBD partition and change all the configs for these systems to point to
the
> new location?

Right.

> 5. Ideally I would have liked a system where all changes including updates
> to packages, config files, data, etc. get mirrored by DRBD, if this is not
> possible how do people prevent the secondary getting out of sync with
> updates. If the primary fails and the secondary takes over it could be out
> of date.

You should mirror the config files with an other tool. E.g. csync2 .
http://oss.linbit.com/csync2/

-phil
--
: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :
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