On Thu, Aug 29, 2013 at 11:11:50AM -0500, Eric Sandeen wrote: > >> Also, I'm curious - I know the code existed before your patch 2/2, > >> but I don't understand why it reserves 1MB for the first superblock > >> when the first superblock is actually at 64k. Any idea? > > > > I'm not sure... According to the git-log, this 1M trick is in > > the following old commit by Chris: > > > > commit a6de0bd778475504f42a142c83b8077993cbddfe > > Author: Chris Mason <chris.mason@xxxxxxxxxx> > > Date: Thu Apr 3 16:35:48 2008 -0400 > > > > Add mirroring support across multiple drives > > Yep I saw that too. Seemingly unrelated. :( Unless I'm missing > something (which I probably am). IIRC the 1 MB of unused space (minus the first superblock) is there to avoid random overwrites from paritioners or somesuch. If the whole megabyte is overwritten including the superblock, the 1st copy lives at 64 MB which exists on practically every fs and the one at 64k can be retored from it. david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
