Re: Postgres, fsync and RAID controller with 100M of internal cache & dedicated battery

On Fri, 24 Aug 2007, Lincoln Yeoh wrote:

> BTW, what happens if someone replaced a faulty battery backed controller card
> on a "live" system with one from a "don't care test system" (identical
> hardware tho) that was powered down abruptly because people didn't care?
> Would the new card proceed to trash the "live" system?

All the caching controllers I've examined this behavior on give each disk
a unique ID, so if you connect new disks to them they wouldn't trash
anything because those writes will only go out to the original drives.
What happens to the pending writes for the drives that aren't there
anymore is kind of undefined though; presumably they'll just be thrown
away, I don't know if there are any cards that try to hang on to them in
case the original disks are connected later.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD