[DRBD-user] DRBD and LVM Snapshot with 2 nodes configuration

Lars Ellenberg Lars.Ellenberg at linbit.com
Wed Apr 7 21:35:07 CEST 2004

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

/ 2004-04-07 21:09:32 +0200
\ Andreas Semt:
> Okay, now I have two possible ways to go, but can I suggest a third way
> (cause I won't use LVM2, so only one way left ...)?
> The situation is:
> nodeA (Heartbeat and drbd active), nodeB (Heartbeat and drbd standby).
> To make a clean and consistent snapshot i will do following (all on nodeB!):
> a) stop heartbeat (at 02.00 pm per cron for example), i.e. that means
>    for heartbeat: "nodeB is dead!, i am the only one left!"
> b) -> result: no further drbd mirroring will be done, the master is
>    still the master (nodeA), nodeA and nodeB knows nothing from each
>    other

What makes you think so?


> Pro: nodeA is still active / services are online
> Con: How to say drbd that is will be shut down in 5 minutes (it is 01:55
> pm, heartbeat/drbd shutdown at 02:00 pm)? Does exists a command for drbd
> to say: "In five minutes you will lost your connection to your primary
> partner, so please write all the stuff in the buffer (of nodeA
> (primary)) and then disconnect and stay on your own"? or to say to the
> primary partner: "Please write all your pending data (from the buffer)
> to your partner (in secondary state), cause that is the last chance if
> you won't like the idea of inconsistent data between you and your partner"?

You keep suggesting the same thing again and again.

No.  And, DBRD does not do any buffering.
It is the file system (that is the mounted file system instance on the
DRBD primary node), that needs to be notified, and there currently just
is no way to do so in a sensible manner. One need to hack up some
existing or new tools, and probably the drbd api too, for this to work.
Could be done. Probably won't be too complicated. Just takes some time
to do it the right way, and nobody has done this so far.

	Lars Ellenberg

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