Hi Miles, Miles Nordin wrote: >>>>>> "ca" == Carsten Aulbert <[EMAIL PROTECTED]> writes: > > ca> (a) Why the first vdev does not get an equal share > ca> of the load > > I don't know. but, if you don't add all the vdev's before writing > anything, there's no magic to make them balance themselves out. Stuff > stays where it's written. I'm guessing you did add them at the same > time, and they still filled up unevenly? >
Yes, they are created all in one go (even on the same command line) and only then are filled - either "naturally" over time or via zfs send/receive (all on Sol10u5). So yes, it seems they fill up unevenly. > 'zpool iostat' that you showed is the place I found to see how data is > spread among vdev's. > > ca> (b) Why is a large raidz2 so bad? When I use a > ca> standard Linux box with hardware raid6 over 16 disks I usually > ca> get more bandwidth and at least about the same small file > ca> performance > > obviously there are all kinds of things going on but...the standard > answer is, traditional RAID5/6 doesn't have to do full stripe I/O. > ZFS is more like FreeBSD's RAID3: it gets around the NVRAMless-RAID5 > write hole by always writing a full stripe, which means all spindles > seek together and you get the seek performance of 1 drive (per vdev). > Linux RAID5/6 just gives up and accepts a write hole, AIUI, but > because the stripes are much fatter than a filesystem block, you'll > sometimes get the record you need by seeking a subset of the drives > rather than all of them, which means the drives you didn't seek have > the chance to fetch another record. > > If you're saying you get worse performance than a single spindle, I'm > not sure why. > No I think a single disk would be much less performant, however I'm a bit disappointed by the overall performance of the boxes and just now we have users where they experience extremely slow performance. But already thanks for the inside Cheers Carsten _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
