[Bugme-janitors] [Bug 6965] New: Kernel doesn't re-sync usb-raid1 after running mdadm --add

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=6965

           Summary: Kernel doesn't re-sync usb-raid1 after running mdadm --
                    add
    Kernel Version: 2.6.18-rc3
            Status: NEW
          Severity: normal
             Owner: io_md at kernel-bugs.osdl.org
         Submitter: kernel at blinkenlights.ch


Most recent kernel where this bug did not occur: 2.6.18-rc2
Distribution: Slackintosh-Current
Hardware Environment:

Mac-Mini (ppc) : Internal Harddisk (rootfs) mirrored to an external
USB2 Harddrive

Problem Description:

The internal harddrive of my MacMini is mirrored to an external
USB2-Harddrive via md-raid1.

Because the kernel doesn't attach the usb-device (sda2) to my
raid (md0) itself (after a reboot) i'm using something like this in my
/etc/rc.d/rc.local:

> #!/bin/sh
> postfix start  (<-- note: postfix ist started before attaching sda2)
> /sbin/mdadm --manage /dev/md0 --add /dev/sda2

This worked well with kernels below 2.6.18-rc2 :
A full sync from hda3 -> sda2 was started after each reboot.

Beginning with 2.6.18-rc2 the kernel didn't sync
the drive after attaching it: It was added to the raid without
a full resync.

According to 'iostat' the kernel does write to both devices
*after* mdadm attached the harddrive but it seems like everything
written to md0 before attaching sda2 will never make it to sda2 :-( :

Example:
--------
mdadm --manage /dev/md0 -f /dev/hda3
mdadm --manage /dev/md0 -r /dev/hda3 #sda2 is now the only active disk of md0
mount /dev/hda3 /mnt/bla
# cat /var/spool/postfix/pid/master.pid 
             649
# cat /mnt/bla/var/spool/postfix/pid/master.pid
             413 <-- ouch!

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