[CentOS] CentOS 4.4 lvm and drbd 0.8?

[Les Mikesell]

Johnny Hughes wrote:
> On Tue, 2007-02-27 at 00:20 -0600, Les Mikesell wrote:
>> Johnny Hughes wrote:
>>> I am not quite sure that drbd-8 is totally ready yet for prime time.
>>> Not that I don't trust them (I use drbd in production and I love it),
>>> but I want to wait for an 8.0.1 or 8.0.2 level before I move the
>>> enterprise CentOS RPMS to that version.
>>>
>>> I would be open to producing some 8.0.0 rpms for testing ... though that
>>> will probably need to wait until after CentOS 5 Beta is released.
>> Could you get the same effect by running software RAID1 with one of the 
>> drives connected via iscsi?
> 
> Provides the same effect as DRBD? ... not really ... as DRBD provides a
> second machine in hot standby mode with a totally synced partition that
> is ready to take over on a failure of the first machine.  If the first
> computer blows up (power supply, hard drive crash, etc.), the second one
> starts up and takes over with no down time (except the time it takes to
> mount the partition and start the services on the new machine).

How is the mirror/sync different than RAID1, and how is DRBD's version
different than you would have if you exported the 2nd machine's 
partitions via iscsi and mirrored the live machine using md devices with 
one local, one iscsi member for each?  If that is actually possible, I'd 
expect those general purpose components too be much better tested and 
more reliable than little-used code like DRBD.   Does DRBD have special 
handling for updating slightly out-of-sync copies or does it have to 
rebuild the whole thing if not taken down cleanly also?

-- 
   Les Mikesell
    lesmikesell at gmail.com