On 9/14/07, Moore, Joe <[EMAIL PROTECTED]> wrote: > I was trying to compose an email asking almost the exact same question, > but in the context of array-based replication. They're similar in the > sense that you're asking about using already-written space, rather than > to go off into virgin sectors of the disks (in my case, in the hope that > the previous write is still waiting to be replicated and thus can be > replaced by the current data)
At one point, I thought this was how data replication should happen too. However, unless you have two consecutive writes to the same space, coalescing the writes could make it so that the data (generically, including fs metadata) on the replication target may be corrupt. Generally speaking, you need to have in-order writes to ensure that you maintain "crash consistent" data integrity in the event of a various failure modes. Of course, I can see how writes could be batched coalesced and applied in a journaled manner such that each batch fully applies or is rolled back on the target. I haven't heard of this being done. Mike -- Mike Gerdts http://mgerdts.blogspot.com/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
