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    SubjectMerging fails reading /dev/uba1
    Hi, Jens:

    I think this question belongs to your domain, but please let me know
    if I'm mistaken, so I can pursue this elsewhere.

    I encountered a strange performance anomaly. I do the following:

    <----- Plug USB key
    [root@lembas ~]# time dd if=/dev/uba of=/dev/null bs=10k count=10240
    10240+0 records in
    10240+0 records out

    real 0m22.731s
    user 0m0.004s
    sys 0m0.345s
    [root@lembas ~]#

    <----- Remove and replug the USB key
    [root@lembas ~]# time dd if=/dev/uba1 of=/dev/null bs=10k count=10240
    10240+0 records in
    10240+0 records out

    real 1m42.622s
    user 0m0.005s
    sys 0m1.518s
    [root@lembas ~]#

    So, reading from a partition of the same device is 5 times slower than
    reading from the device itself. The question is, why?

    To the best of my knowledge, this does not occur with SCSI (usb-storage
    and sd or sr). This hints strongly that the ub is not doing something
    right, but what that can be?

    The ub takes the request processing machinery from Carmel exactly. I am
    wondering if Carmel (sx8) exhibits any similar performance anomalies
    (cc-ing to Jeff)

    Additional information:

    [root@lembas ~]# cat /proc/version
    Linux version 2.6.11-rc4-lem (zaitcev@lembas) (gcc version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)) #1 Tue Feb 15 23:06:39 PST 2005
    [root@lembas ~]# cat /proc/partitions
    major minor #blocks name

    3 0 39070080 hda
    3 1 5935986 hda1
    3 2 5936017 hda2
    3 3 554242 hda3
    3 4 1 hda4
    3 5 26643771 hda5
    180 0 1024000 uba
    180 1 1023983 uba1
    [root@lembas ~]#

    Thanks,
    -- Pete
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