zfs discuss - Aug 2009 - ub_guid_sum and vdev guids

I''ve a zfs pool named ''ppool'' with two vdevs(files)
file1, file2 in it.

zdb -l /pak/file1 output:
    version=16
    name=''ppool''
    state=0
    txg=3080
    pool_guid=14408718082181993222
    hostid=8884850
    hostname=''solaris-b119-44''
    top_guid=4867536591080553814
    guid=4867536591080553814
    vdev_tree
        type=''file''
        id=0
        guid=4867536591080553814
        path=''/pak/file1''
        metaslab_array=23
        metaslab_shift=19
        ashift=9
        asize=68681728
        is_log=0


zdb -l /pak/file2 output:
    version=16
    name=''ppool''
    state=0
    txg=3081
    pool_guid=14408718082181993222
    hostid=8884850
    hostname=''solaris-b119-44''
    top_guid=4015976099930560107
    guid=4015976099930560107
    vdev_tree
        type=''file''
        id=1
        guid=4015976099930560107
        path=''/pak/file2''
        metaslab_array=27
        metaslab_shift=19
        ashift=9
        asize=68681728
        is_log=0


bash-3.2# zdb -uuu ppool
Uberblock

        magic = 0000000000bab10c
        version = 16
        txg = 3082
        guid_sum = 4845486699483555527

I see that the uber block ub_guid_sum is not equal to the sum of guid''s
of both the vdevs. Can someone please explain me why?

Regards,
pak
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This message posted from opensolaris.org

14408718082181993222 + 4867536591080553814 - 2^64 + 4015976099930560107 =
4845486699483555527

there was an overflow inbetween, that I overlooked.

pak
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This message posted from opensolaris.org