[DRBD-user] "Concurrent local write detected!"

Chris Worley worleys at gmail.com
Thu Dec 30 00:13:56 CET 2010

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

On Wed, Dec 29, 2010 at 3:28 PM, Dan Barker <dbarker at visioncomm.net> wrote:
>> From: drbd-user-bounces at lists.linbit.
>> Sent: Wednesday, December 29, 2010 4:49 PM
>> I really think drbd is being brain-dead here.  Concurrent writes to
>> the same LBA aren't an issue... just do it!  Note the below is using a
>> primary/secondary setup on two raw drbd devices; no GFS anywhere.
> <snip>
> But the result is undefined! What should DRBD write to the other member? The
> result of the first or the second write?
> You are using a tool that permits the execution of stupid I/O streams. Good
> for stress testing, but not good for data integrity. If you want undefined
> data on a DRBD pair, then disconnect before the I/O, do the undefined thing,
> and upon reconnect DRBD will faithfully replicate the garbage. It will still
> be  undefined stuff, but it will be identical undefined stuff.
Are you seriously thinking that Unix doesn't allow two writes to the
same LBA simultaneously?

This is part of Unix file system semantics.

A dead system is not the proper outcome.


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