[DRBD-user] drbd implementation question

Ross S. W. Walker rwalker at medallion.com
Fri Oct 19 15:53:20 CEST 2007

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

Kelly Byrd wrote:
> On Thu, 18 Oct 2007 18:48:56 +0200, "Rudi Ahlers" 
> <Rudi at SoftDux.com> wrote:
> > Hi all
> > 
> > I'm new to drbd and have some questions, hoping someone 
> could help me.
> I'd
> > like to use software RAID & LVM to make it easier to upgrade in the
> future.
> > 
> > how do I manage such a setup?
> > Do I first setup the RAID, then the LVM volumes and the drbd?
> > Can I install & setup drbd on partitions with existing data?
> > 
> What are you looking for in the end? One big replicated chunk
> of space? Do you need smaller granularity? For the local
> RAID, what are the requirements there? RAID0? RAID5? RAID1? 
> If you're going to run raid and lvm underneath drbd, I'm not
> sure how you'll keep existing data. Wouldn't creating LVMs on
> top of an  existing partition with data in it destroy that
> filesystem?
> I'm pretty sure you can't directly create a drbd with existing
> data,  drbd is a block device, so it would run underneath a
> filesystem. If you had a filesystem with data in it already,
> making a drbd out of that space would screw up the filesystem
> and the data. Just like when you create a RAID1 from existing
> data, you copy the data into the RAID1.

Create the RAID, whether it is HW or SW.

Create a LVM VG out of the RAID array(s).

Create LVM LVs out of the VG.

You can create a drbd volume after the fact, you just CANNOT
create it with the meta-data on that volume you have to locate
the meta-data on a separate volume.

I prefer to locate the meta-data separately anyways, I create
a separate LV for drbd meta-data, and do drbd per-LV instead
of per RAID array.


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