> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Jim Klimov > > Thanks... but doesn't your description imply that the sync writes > would always be written twice?
That is correct, regardless of whether you have slog or not. In the case of slog, it gets written first to a dedicated device, and then to the pool. In the case of no-slog, it gets written to dedicated ZIL recyclable blocks in the main pool, and then it gets written to the main pool again as part of the next TXG. All of this is true, except when the sync write is sufficiently large. When it's larger than a configurable threshold (I forget which parameter, but I could look it up) then it goes directly to the main pool and skips the ZIL completely. I don't know how exactly that is implemented - Maybe it goes into the next TXG and simply forces the next TXG to flush immediately. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
