We've recently been trying to certify DRBD (we've tried both 0.7.5 and 
0.7.10 with the same results) on ppc64 with RHEL3.

Unfortunately, we have run into two fairly serious issues:

1) we had to hack up the source just to get it to build:

The basic problem is that the adjust_drbd_config_h.sh script is not 
doing the right thing for RHEL3 on ppc64. RHEL3 has a find_next_bit() 
function, and on most architectures it's an inline function. However, on 
ppc64 it's not inline and it's not exported, which means drbd (being a 
module) can't use it. So we have to actually disable the 
HAVE_FIND_NEXT_BIT setting in drbd_config.h. Also, there is no 
arch-specific find_next_bit function for ppc64 in drbd_compat_types.h, 
so we have to use the generic find_next_bit function that's in that file 
(by defining USE_GENERIC_FIND_NEXT_BIT in drbd_config.h). Of course, 
when this function is defined, it conflicts with the previous 
find_next_bit function declaration from the kernel headers 
(asm-ppc64/bitops.h). So, we had to rename the generic function to 
generic_find_next_bit and change all calls in the drbd source (just one 
in drbd_bitmap.c) to use generic_find_next_bit instead of find_next_bit.


2) additionally, the driver appears to start up fine on both machines, 
but when the resync begins, it quickly stalls and never makes any progress


Included are the DRBD config and other system information. Please let me 
know if you need any further information.

Thanks,
Paul


--------
After starting drbd on the source system (already running on the 
target), this happens:

[root@trumpkin root]# cat /proc/drbd
version: 0.7.5 (api:76/proto:74)
SVN Revision: 1578 build by root@tumnus, 2005-04-29 10:13:28
  0: cs:SyncSource st:Secondary/Secondary ld:Consistent
     ns:128 nr:0 dw:0 dr:128 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
         [>...................] sync'ed:  0.9% (978816/978944)K
         finish: 2:43:08 speed: 32 (32) K/sec

[root@trumpkin root]# cat /proc/drbd
version: 0.7.5 (api:76/proto:74)
SVN Revision: 1578 build by root@tumnus, 2005-04-29 10:13:28
  0: cs:SyncSource st:Secondary/Secondary ld:Consistent
     ns:128 nr:0 dw:0 dr:128 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
         [>...................] sync'ed:  0.9% (978816/978944)K
         finish: 7:28:37 speed: 8 (8) K/sec

[root@trumpkin root]# cat /proc/drbd
version: 0.7.5 (api:76/proto:74)
SVN Revision: 1578 build by root@tumnus, 2005-04-29 10:13:28
  0: cs:SyncSource st:Secondary/Secondary ld:Consistent
     ns:128 nr:0 dw:0 dr:128 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
         [>...................] sync'ed:  0.9% (978816/978944)K
         finish: 8:09:24 speed: 8 (8) K/sec

[root@trumpkin root]# uname -a
Linux trumpkin 2.4.21-27.EL #1 SMP Wed Dec 1 21:53:20 EST 2004 ppc64 
ppc64 ppc64
  GNU/Linux


--------
On the target, this is reported:

[root@tumnus root]# cat /proc/drbd
version: 0.7.5 (api:76/proto:74)
SVN Revision: 1578 build by root@tumnus, 2005-04-29 10:13:28
  0: cs:SyncTarget st:Secondary/Secondary ld:Inconsistent
     ns:0 nr:128 dw:128 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
         [>...................] sync'ed:  0.9% (978816/978944)K
         finish: 106:02:18 speed: 0 (0) K/sec

[root@tumnus root]# cat /proc/drbd
version: 0.7.5 (api:76/proto:74)
SVN Revision: 1578 build by root@tumnus, 2005-04-29 10:13:28
  0: cs:SyncTarget st:Secondary/Secondary ld:Inconsistent
     ns:0 nr:128 dw:128 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
         [>...................] sync'ed:  0.9% (978816/978944)K
         finish: 117:35:37 speed: 0 (0) K/sec

[root@tumnus root]# cat /proc/drbd
version: 0.7.5 (api:76/proto:74)
SVN Revision: 1578 build by root@tumnus, 2005-04-29 10:13:28
  0: cs:SyncTarget st:Secondary/Secondary ld:Inconsistent
     ns:0 nr:128 dw:128 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0
         [>...................] sync'ed:  0.9% (978816/978944)K
         finish: 118:16:24 speed: 0 (0) K/sec

[root@tumnus root]# uname -a
Linux tumnus 2.4.21-27.EL #1 SMP Wed Dec 1 21:53:20 EST 2004 ppc64 ppc64 
ppc64 GNU/Linux