Neil Perrin writes: > Yes James is right this is normal behaviour. Unless the writes are > synchronous (O_DSYNC) or explicitely flushed (fsync()) then they > are batched up, written out and committed as a transaction > every txg_time (5 seconds). > > Neil. > > James C. McPherson wrote: > > Bob Evans wrote: > > > >> Just getting my feet wet with zfs. I set up a test system (Sunblade > >> 1000, dual channel scsi card, disk array with 14x18GB 15K RPM SCSI > >> disks) and was trying to write a large file (10 GB) to the array to > >> see how it performed. I configured the raid using raidz. > >> > >> During the write, I saw the disk access lights come on, but I noticed > >> a peculiar behavior. The system would write to the disk, but then > >> pause for a few seconds, then contineu, then pause for a few seconds. > >> > >> > >> I saw the same behavior when I made a smaller raidz using 4x36 GB > >> scsi drives in a different enclosure. > >> > >> Since I'm new to zfs, and realize that I'm probably missing > >> something, I was hoping somebody might help shed some light on my > >> problem. > > > > > > Hi Bob, > > I'm pretty sure that's not a problem that you're seeing, just > > ZFS' normal behaviour. Writes are coalesced as much as possible, > > so the "pauses" that you observed are most likely going to be > > the system waiting for suitable IOs to be gathered up and sent > > out to your storage. > > > > If you want to examine this a bit more then might I suggest the > > DTrace Toolkit's iosnoop utility. > > > > > > best regards, > > James C. McPherson > > _______________________________________________ > > zfs-discuss mailing list > > zfs-discuss@opensolaris.org > > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > > > -- > > Neil > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
I also would agree if the application is burning 100% of a CPU. But if the application is being throttled at times _and_ the storage is itself not 100% exercised then I believe something is wrong and we have that anomalous jumpyness. So Bob, is the application burning a full CPU ? -r _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
