[DRBD-user] size in drbd.conf and size of drbd0 should be the same?

Casey Allen Shobe cshobe at bepress.com
Thu Aug 28 20:21:56 CEST 2008

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

On Aug 28, 2008, at 1:57 AM, Alex wrote:
> And i am using it to have better control over drbd devices. I am  
> running LVM
> on top of drbd0 and GFS on top of LVM. GFS does not support  
> shrinking. In any
> scenario, I don't want to be suprissed when i'm replacing disks and  
> drbd are
> resizing drbd0 on the fly. GFS could be corrupted. Even if disks  
> (raid5 or
> raid6 arrays) will be the same in size, this is not a must to be  
> identical.
> So, shortly, i don't want to give permission to drbd to adjust the  
> size on
> the fly (to avoid shrinking). I want to have full controll regarding  
> drbd
> size and all the time i am setting it in drbd.conf with 5-10% less  
> then
> minimum available hardware size available on our nodes.

That doesn't really make sense.  DRBD does not magically try to shrink  
your filesystems on the fly.  I belive the place to set the size 5-10%  
lower than hardware is at the first level above the hardware - below  
LVM even - just set the LVM partition in fdisk to be 5-10% less than  
available and that's all you should have to worry about.  Then you can  
forget about the size directive.

> And my question comes naturally, because i want to be sure that i am  
> using the
> correct syntax. Probably, "size" directive is the correct one to be  
> used in
> newer drbd versions and "disk-size" syntax is deprecated (has been  
> used on
> old drbd implementations).
> Can somebody clarify this aspect?

According to the documentation you just sent a link to, size should  
exist within a disk section if used at all.  Though I see reference to  
it in the disk section, there is no documentation of it otherwise.  So  
I'm really curious how you're deducing that this will give you some  
control that is not documented anywhere - are you just guessing or is  
this discussed elsewhere I haven't seen?

Casey Allen Shobe
Database Architect, The Berkeley Electronic Press
cshobe at bepress.com (email/jabber/aim/msn)
http://www.bepress.com | +1 (510) 665-1200 x163

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