[DRBD-user] DRDB on one host

Csanad Novak csanad at pixelfusion.co.nz
Tue May 13 23:47:19 CEST 2014

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

Hi Arnold,

I guess the challenge here is that the instance-storage get reseted completely (back to the point when its just a raw device without partitions) on every stop/start cycle.

Currently I’m using a less than satisfactory solution on non critical servers, as follow:

I’ve got mounted my instance-storage as /dev/sdb1 to /var
I’ve got mounted my ebs device as /dev/sdc1 to /mnt/var-backup

I’ve lsyncd configured to sync from /var to /mnt/var-backup

I’ve wrote a little bash script for auto partitioning and mounting. When the instance get stopped for any reason the instance storage gets reseted and the whole /var directory destroyed. After boot up my script repartitioning the instance storage, mount it, and then automatically rsync back the data from /mnt/var-backup.

There is several issue with this architecture, but the biggest one with lsyncd, which wasn’t designed for this. If I cloud change lsyncd to drbd, that would great.

I must stress again: instance-storage is a local hard-disk based block device, while the ebs storage is a network attached block device.



From: Arnold Krille arnold at arnoldarts.de
Reply: Arnold Krille arnold at arnoldarts.de
Date: 14 May 2014 at 6:18:25
To: drbd-user at lists.linbit.com drbd-user at lists.linbit.com
Subject:  Re: [DRBD-user] DRDB on one host  

On Tue, 13 May 2014 09:57:21 +1200 Csanad Novak  
<csanad at pixelfusion.co.nz> wrote:  
> Recently on the latest AWS Summit I’ve seen an interesting setup for  
> utilising the AWS EC2 instance storage. The instance storage is the  
> local filesystem on the Amazon cloud, unfortunately it is not  
> persistent - all data get lost if the instance stops. For persistent  
> storage one must use an so called EBS volume, which is a network  
> attached block device. Unfortunately the EBS storage performance is  
> varies, depending on the neighbour instances’ traffic. An ideal world  
> one can use the instance storage without the worry of data loss.  
> On the latest AWS Summit a presenter proposed an architecture where  
> the instance storage was utilised and was synced with DRBD to the EBS  
> block  
> device. http://www.slideshare.net/AmazonWebServices/so-you-think-you-are-an-aws-ninja-dean-samuels -  
> slide 11.  
> I wonder how an example config would looks like. I went trough  
> quickly on the tutorials, but couldn’t find any example with one host  
> setup.  

drbd on one host. Isn't that what raid/md is?  

I haven't had a chance to play with aws but if both ebs volumes and the  
instance-storage are block devices, it should be easy to mirror them  
with md or lvm.  

- Arnold  
drbd-user mailing list  
drbd-user at lists.linbit.com  
Kind regards,

Csanad Novak
Technical Lead
P / 09 353 1234
M / 021 060 1531
E / csanad at pixelfusion.co.nz 
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