drbd-user March 2010 archive
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drbd-user: Re: [DRBD-user] bringing up drbd-device in primary ro

Re: [DRBD-user] bringing up drbd-device in primary role during execution of linuxrc during boot up?

From: Henrik Kuhn <henrik.kuhn_at_nospam>
Date: Fri Mar 05 2010 - 09:56:45 GMT
To: drbd-user@lists.linbit.com

>> Does anybody know what kind of configuration setup is necessary on
>> openSUSE 11.1 to bring a drdb-device into primary role during the
>> execution of the initrd linuxrc-script?
>> The purpose would be that on one node a drbd-device gets primary before
>> fsck checks the underlying FS during system boot and the device is ready
>> for auto-mounting via fstab.
>>
>> So far I have figured out: Because drbd needs the /etc/drbd.conf, it is
>> not sufficient to add the drbd-module to the INITRD_MODULES list and run
>> 'mkinitrd', because the mkinitrd scripts are missing for handling drdb
>> specific tasks during generation of the initial ramdisk.
>>
>> Is it possible to add the necessary drbd items manually to an existing
>> initrd?
>>
> You probably won't like my comment:
> Don't do that.
>
> Do not try to activate drbd from your initrd.
> Simply don't.
> It is in almost every case the completly wrong approach.
>
>
> But, maybe you have a very good reason
> to try to activate drbd from your initrd,
> so please, what exactly are you up to?
>
>
Hm, can you tell me/us why it is not advisable to activate drbd right
out of initrd?

I was thinking of the device mapper (LVM, softRAID, ...) which is
capable to come up during initial boot. That is the user can rely on the
devices already activated and ready for usage, even fsck had been taken
place. Why wouldn't it be possible to do the same with drdb?
Of course I can bring up the system first and add another init-script to
bring a drbd-device first up to primary role, then mount it and then
start e.g. NFS. Or I change the dependencies of the init-scripts.
Especially in this case I just want to use drbd as a 'simple' networked
RAID1, where a replicate is on a different node to have a worst case
backup of 1,5 TB of data. That is the primary role won't switch from one
node to the other. The drdb-device on Node1 is always primary and
directly available upon reboot.

Henrik

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