additional clarification ... On Jan 14, 2010, at 8:49 AM, Richard Elling wrote:
> On Jan 14, 2010, at 6:41 AM, Gary Mills wrote: > >> On Thu, Jan 14, 2010 at 01:47:46AM -0800, Roch wrote: >>> >>> Gary Mills writes: >>>> >>>> Yes, I understand that, but do filesystems have separate queues of any >>>> sort within the ZIL? If not, would it help to put the database >>>> filesystems into a separate zpool? >>>> >>> >>> The slog device is for the pool but the ZIL is per >>> filesystem/dataset. The logbias property can be used on a dataset to >>> prevent that set from consuming the slog device resource : >>> >>> http://blogs.sun.com/roch/entry/synchronous_write_bias_property >> >> Ah, that's what I wanted to know. Thanks for the response. > > Roch, I think this can be misinterpreted, so perhaps more clarity is needed. > > If you have sync writes, they will be written to persistent storage before > they are acknowledged. > > The only question is where they will be written: to the ZIL or pool? > > By default, this preference is based on the size of each I/O, with small > I/Os written to the ZIL and large I/Os written to the pool. > > The dataset parameter logbias is used to set the ZIL vs pool preference. > > Thus, one could force all datasets, save one, to use the pool and permit > the one, lucky dataset to use the ZIL (or vice versa) Should read: Thus, one could force all datasets, save one, to use the pool and permit the one, lucky dataset to use the ZIL (or vice versa) for large I/Os. -- richard > Separate log devices is an orthogonal issue. > -- richard > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
