[DRBD-user] URGENT Request for DRBD Developers

Johnny Hughes mailing-lists at hughesjr.com
Sat May 24 02:17:57 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.


Art Age Software wrote:
>> when the upgrade from 8.0 to 8.2 is no longer
>> automatic because of protocol changes, then you MIGHT appreciate my decision
>> a bit more ... but then again, maybe you won't.
> 
> I'm not sure about this. If the protocol changes in a future version
> of 8.2, would that not affect current 8.2 users just as much as 8.0
> users? In which case, the upgrade would not be "automatic" for 8.2
> users either.
> 

The difference might be caused by this rule:
Note: "api" version denotes compatibility level to the user space tool 
drbdsetup. Identical "proto" number means these are compatible on the 
wire, so to upgrade you could connect two different releases with the 
same proto version.

Since drbd 0.7.0, two drbd releases with adjacent api versions will be 
able to talk with each other, which makes rolling upgrades (no service 
downtime) possible.

======
My point is that incremental upgrades (like from 8.2.5 to 8.2.6) are 
going to almost always going to be designed to be able to be done ... 
but eventually as the api/proto on 8.0.x stays the same AND as 8.2.x 
continues to increase the chances are the the API will diverge by more 
than one between 8.0.x and 8.2.x, and at that point a move from 8.0.x to 
8.2.x will become hard.  There is the possibility that the divergence 
will grow to be fairly large (unless the devels prevent it somehow) ... 
and in several years, when 8.0 support ends, and upgrade to 8.2 could be 
considerably harder ... like the update from 0.7.x to 0.8.x is now.

That is one of the factors that went into the decision.

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