[DRBD-user] /dev/drbd0 incorrect size

Mike Lovell mike at dev-zero.net
Thu Apr 29 09:51:04 CEST 2010

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


Chad Sine wrote:
> DRBD Users,
>
> I'm setting up 2 CentOS 5.4 x86_64 servers to use DRBD.  I set them up 
> to do RAID1, but /dev/drbd0 only shows up at 12GB instead of the 1.8 
> TB that the underlying devices have.
>
> Both boxes are configured just like this, with 1800GB for /dev/sda4
>
> [root at centos54 etc]# parted
> GNU Parted 1.8.1
> Using /dev/sda
> Welcome to GNU Parted! Type 'help' to view a list of commands.
> (parted) print
>
> Model: Dell VIRTUAL DISK (scsi)
> Disk /dev/sda: 2000GB
> Sector size (logical/physical): 512B/512B
> Partition Table: msdos
>
> Number  Start   End     Size    Type     File system  Flags
>  1      32.3kB  206MB   206MB   primary  ext3         boot
>  2      206MB   108GB   107GB   primary  ext3
>  3      108GB   120GB   12.8GB  primary  ext3
>  4      120GB   1920GB  1800GB  primary
>
> Here is the /etc/drbd.conf used on each
>
> global { usage-count no; }
> common { syncer { rate 1000M; } }
> resource drbd-data {
>         protocol C;
>         startup {
>                 wfc-timeout  15;
>                 degr-wfc-timeout 60;
>                 become-primary-on centos54;
>         }
>
> #       disk {
> #               size 1700G;
> #       }
>         net {
>                 cram-hmac-alg sha1;
>                 shared-secret "myP4$$";
>         }
>         on centos54 {
>                 device /dev/drbd0;
>                 disk /dev/sda3;
>                 address 10.0.0.1:7787 <http://10.0.0.1:7787>;
>                 meta-disk internal;
>         }
>         on centos54_2 {
>                 device /dev/drbd0;
>                 disk /dev/sda3;
>                 address 10.0.0.2:7787 <http://10.0.0.2:7787>;
>                 meta-disk internal;
>         }
> }
>
> From there, I ran the following command to create the md on each box
> # drbdadm create-md drbd-data
>   
>
> Then I ran the following command on the primary system
> # drbdadm -- --overwrite-data-of-peer primary drbd-data
>   
> Everything looks to synchronize with UpToDate for each device and 
> centos54 is primary.
>
> However, now if I run parted on /dev/drbd0, it is only 12 GB, instead 
> of 1.8TB.  I tried doing the following, but I still only get a 12GB 
> partition
>
> # mkfs.ext3 /dev/drbd0
> # mount /dev/drbd0 /media
>
> What can I do to get the full 1.8 TB of mirrored storage?  
> Unfortunately, I don't have the output of the last few commands 
> available, sine the server is in use at the moment.  I'll be able to 
> test and give proper output this weekend, when I swap out hard drives 
> and attempt this transition again.

according to the output of parted, sda3 is 12.8GB in size and, what do 
ya know, you told drbd to use /dev/sda3 for the disk of the drbd-data 
resource. so it did exactly what you told it. if you want to use the 
1.8TB, change drbd to use sda4.

mike
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