[DRBD-user] Multi-disk devices possible?

Sebastian spa at syntec.co.uk
Fri Jun 3 12:26:29 CEST 2011

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


Felix Frank wrote:
> On 06/03/2011 11:06 AM, Sebastian wrote:
>> Then we have ESXi on top, so the disks are virtualized.
> 
> So you're running DRBD inside a vmWare guest?

Yes.  It is arguable whether I still require it virtualized (at least on
both nodes), but it is.  Do you think I would see much performance benefit
from running my O/S (see next para for details) directly on the bare metal?

>> I presume that to do this I would need to break my existing DRBD
>> set-up and possibly lose all the data on it?  How can I do this
>> without losing the data?  Can I make the cluster stand-alone,
>> reconfigure one of the nodes to use an LVM Volume as my backing
>> device, make that one the primary, wait until it resyncs, do the
>> same on the other node, then extend the DRBD device, and then extend
>> the filesystem? 
> 
> What is the current layout and DRBD usage?

DRBD is being used as part of Openfiler to produce a HA cluster for NAS
storage.  The current layout on node1 is:
/dev/sda ~ 8 GB - O/S disk
/dev/sdb1 ~ 512 MB - /dev/drbd0 - used for cluster_metadata
/dev/sdb2 ~ 1 TB - /dev/drbd1 (actually LVM so /dev/mapper/vg0drbd-filer) -
used for NAS
/dev/sdc1 ~ 1 TB - /dev/mapper/tempnas-tempnasv LV - temporary storage, has
90% of the data contained on /dev/sdb2 - I want to reformat this disk and
add it to /dev/drbd1, well /dev/mapper/vg0drbd-filer.

Hmm, that gives me an idea.  I suppose because the data is using LVM, I
could create a new drbd device and add it to the same LV,
/dev/mapper/vg0drbd-file, right?  What would be the benefits and
disadvantages of splitting 1 mounted LV filesystem over 2 DRBD devices?

The current layout on node2 is:
/dev/sda ~ 8 GB - O/S disk
/dev/sdb1 ~ 512 MB - /dev/drbd0 - used for cluster_metadata
/dev/sdb2 ~ 1 TB - /dev/drbd1 (actually LVM so /dev/mapper/vg0drbd-filer) -
used for NAS
/dev/sdc1 ~ 1 TB - unformatted.

> You could get away with doing this online.
> 
> 1. Create VG on secondary (with free disks, assuming you have those)
> 2. take secondary offline, dd everything to an LV in the new VG
> 3. bring secondary back, using the new LVM backing device
> 4. promote secondary, repeat on former primary
> 5. scrub former backing devices, include in VG and expand LVs
> as desired
> 6. resize the DRBD as explained in the User's Guide

Sounds like that should work.  When you say "scrub", I presume that is
optional?  Or how should I do that?

> Cheers,
> Felix

Many thanks,

Sebastian




More information about the drbd-user mailing list