Re: RAID0 DeviceDisappeared event happen when restart mdmonitor service

[NeilBrown <neilb@suse.de>]

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On Mon, 17 Sep 2012 10:30:49 +0800 Jack Wang <jack.wang.usish@gmail.com>
wrote:

> I check into code in mdmonitor.c in function check_array:
> 
> 	fd = open(dev, O_RDONLY);
> 	if (fd < 0) {
> 		if (!st->err)
> 			alert("DeviceDisappeared", dev, NULL, ainfo);
> 		st->err=1;
> 		return 0;
> 	}
> 	fcntl(fd, F_SETFD, FD_CLOEXEC);
> 	if (ioctl(fd, GET_ARRAY_INFO, &array)<0) {
> 		if (!st->err)
> 			alert("DeviceDisappeared", dev, NULL, ainfo);
> 		st->err=1;
> 		close(fd);
> 		return 0;
> 	}
> 	/* It's much easier to list what array levels can't
> 	 * have a device disappear than all of them that can
> 	 */
> 	if (array.level == 0 || array.level == -1) {
> 		if (!st->err)
> 			alert("DeviceDisappeared", dev, "Wrong-Level", ainfo);
> 		st->err = 1;
> 		close(fd);
> 		return 0;
> 	}
> 
> I suspect above code lead to the DeviceDisapeared event you see, not
> sure why this get GET_ARRAY_INFO return array.level == 0 means Device
> Disappeared?
> 
> Anyone who more familiar with the logic may gave a comment?


It isn't possible or meaningful to monitor RAID0 devices - there is nothing
to see, nothing that can happen, nothing to report.

mdadm will normally completely ignore RAID0 devices.

If you run
  mdadm --monitor /dev/md1

when md1 is a RAID0 device, then it will be required to actively forget about
it, so it reports that the device has disappeared (because it was on the
list, but now isn't).

This shouldn't happen if you run "mdadm --monitor --scan" which is the
standard usage.  It that what is happening?

NeilBrown



> 
> 
> Best regards!
> 
> Jack
> 
> 2012/9/14 Johnson Yan <johnson_yan@usish.com>:
> > Hi All,
> > When I restart mdmonitor service, a notify email will be received, which
> > indicate DeviceDisappeared event happened for RAID0, is this phenomenon
> > reasonable? Could anyone explain this?
> >
> >
> > The email info as below
> > ......
> > Host            : host3.com
> > Event           : DeviceDisappeared
> > MD Device       : /dev/md1
> > ......
> >
> > [root@host3 ~]# service mdmonitor restart
> > Killing mdmonitor:                                         [  OK  ]
> > Starting mdmonitor:                                        [  OK  ]
> > [root@host3 ~]#
> > [root@host3 ~]# cat /proc/mdstat
> > Personalities : [raid1] [raid0]
> > md1 : active raid0 sda1[1] sdb1[0]
> >       927933312 blocks super 1.2 64k chunks
> >
> > md2 : active raid1 sdc1[1] sde1[0]
> >       292836160 blocks super 1.2 [2/2] [UU]
> >       bitmap: 0/2 pages [0KB], 131072KB chunk
> >
> > md0 : active raid1 sdf1[0] sdg1[1]
> >       488254272 blocks super 1.2 [2/2] [UU]
> >       bitmap: 0/2 pages [0KB], 131072KB chunk
> >
> > unused devices: <none>
> > [root@host3 ~]#
> > [root@host3 ~]# uname -r
> > 3.2.28-11.el6.x86_64
> > [root@host3 ~]#
> > [root@host3 ~]# mdadm -V
> > mdadm - v3.2.5 - 18th May 2012
> > [root@host3 ~]#
> >
> >
> > Thanks in advance.
> > Johnson Yan
> >
> >
> > --
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