Mike Snitzer wrote:

On 7/26/06, Paul Clements [off-list ref] wrote:

quoted

Right. At the time of the failover, there were (probably) blocks that
were out of sync between the primary and secondary.

OK, so now that I understand the need to merge the bitmaps... the
various scenarios that create this (potential) inconsistency are still
unclear to me when you consider the different flavors of raid1.  Is
this inconsistency only possible if using async (aka write-behind)
raid1?

No. Even with a synchronous (normal) raid1, you will probably have 
blocks that are out of sync when one disk (or server) fails. This is 
true even of raid1's using internal disks. That's why you resync the 
array after a failure (of the system or of one of the disks). That's 
exactly what the bitmap is for -- to optimize that resync.

--
Paul