[Linux-cluster] Re: [Iscsitarget-devel] Problem in clvmd and iscsi-target

[Nuno Fernandes]

On Thursday 03 April 2008 15:56:52 Ross S. W. Walker wrote:
> You have given lots of LVM info, but no iscsi-target info.
>
> What version? A copy of your ietd.conf. Output of /proc/net/iet/volume
Sorry :)

iscsitarget-0.4.16-1

ietd.conf
Target iqn.2007-04.com.eurotux.dc.gray:storage.disk.hdb
        Lun 0 Path=/dev/hdb,Type=blockio,ScsiId=95afc14465efeb27
        Alias Test
        InitialR2T              No
        ImmediateData           Yes
        MaxRecvDataSegmentLength 16384
        MaxXmitDataSegmentLength 16384
        #MaxBurstLength         262144
        #FirstBurstLength       65536
        MaxOutstandingR2T       8
        Wthreads                8

Output of proc data:
tid:1 name:iqn.2007-04.com.eurotux.dc.gray:storage.disk.hdb
        lun:0 state:0 iotype:blockio iomode:wt path:/dev/hdb

Meanwhile i narrow it down to a iscsi-target problem. Doing strace i saw it 
requires exclusive open. So solve it it created an sort of an hack.. :)

from hdb and using device-mapper i create a linear mapping to 2 devices:

hdb-int
hdb-ext

Next i put hdb-ext in ietd.conf and hdb-int in lvm.conf. iscsi-target still 
opens in exclusive mode but it only opens hdb-ext device.
clvmd uses hdb-int that has no exclusive lock.

Another way that we rejected is to put "gray" machine exporting the iscsi 
volume to it self also and using that device in clvmd. This option also 
worked but has less performance as all local contend has to be encoded to 
iscsi and decoded in the same machine.

The problem of iscsi-target opening the device excluse remais.

Thanks,
Nuno Fernandes


>
> If you export /dev/hdb via iscsi it will not be accessible for anything
> else.
>
> -Ross
>
>
> ----- Original Message -----
> From: iscsitarget-devel-bounces at lists.sourceforge.net
> <iscsitarget-devel-bounces at lists.sourceforge.net> To: 'linux clustering'
> <linux-cluster at redhat.com>; iscsitarget-devel at lists.sourceforge.net
> <iscsitarget-devel at lists.sourceforge.net> Sent: Thu Apr 03 10:25:25 2008
> Subject: [Iscsitarget-devel] Problem in clvmd and iscsi-target
>
> Hi,
>
> There is a race condition in iscsi-target and clvmd that does not allow me
> to export a volume by iscsi and use it localy in clvmd.
>
> I have two servers "black" and "gray". "Gray" has two drives hda (for
> filesystem) and hdb (that is going to be exported through iscsi to
> "black"). Then both machines are part of a 2 node cluster to use clvmd.
>
> root gray ~ # /etc/init.d/iscsi-target start
> Starting iSCSI target service:                             [  OK  ]
> root gray ~ # /etc/init.d/clvmd start
> Starting clvmd:                                            [  OK  ]
> Activating VGs:   No volume groups found
>                                                            [  OK  ]
> root gray ~ # pvcreate /dev/hdb
>   Can't open /dev/hdb exclusively.  Mounted filesystem?
> root gray ~ # /etc/init.d/iscsi-target stop
> Stopping iSCSI target service:                             [  OK  ]
> root gray ~ # pvcreate /dev/hdb
>   Physical volume "/dev/hdb" successfully created
> root gray ~ #
>
> I cannot use clvmd and iscsi-target on the same machine? If i create a
> logical volume is is activated in "black"
>
> lvdisplay -C
>   LV     VG    Attr   LSize   Origin Snap%  Move Log Copy%
>   teste2 teste -wi-a-   1.00G
>
> and in "gray" is disabled:
>
> root gray ~ # lvdisplay -C
>   LV     VG    Attr   LSize Origin Snap%  Move Log Copy%
>   teste2 teste -wi-d- 1.00G
>
> Any ideas?
>
> Thanks
> Nuno Fernandes
>
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