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) Separate log devices is an orthogonal issue. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
