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[Linux-cluster] RE: LVM Mirror in clustered environments



Hi,

 

After some additional testing I’ve checked that the problem is related with dm-multipath, using /dev/sd devices instead of the multipath devices everything went fine.

 

Is cmirror supposed to work fine with dm-multipath or is it not supported?, is this a bug?

 

Best regards,

 

Alfredo

 

 

 


From: linux-cluster-bounces redhat com [mailto:linux-cluster-bounces redhat com] On Behalf Of Moralejo, Alfredo
Sent: Monday, August 24, 2009 6:12 PM
To: linux-cluster redhat com
Subject: [Linux-cluster] LVM Mirror in clustered environments

 

Hi,

 

I’m testing clustered mirror with RHEL 5.3 and I’m finding weird behavior. I’ve installed and enabled cmirror and created a couple of mirrored logical volumes (after some fight with clvmd errors…):

 

[root rmamseslab07 usr]# lvs -a -o +devices

  lvol8                vg00      -wi-ao 4.00G                                                  /dev/cciss/c0d0p2(736)                    

  lv_mirror            vgcluster mwi-ao 1.00G                    lv_mirror_mlog 100.00         lv_mirror_mimage_0(0),lv_mirror_mimage_1(0)

  [lv_mirror_mimage_0] vgcluster iwi-ao 1.00G                                                  /dev/mapper/mpath0p2(0)                   

  [lv_mirror_mimage_1] vgcluster iwi-ao 1.00G                                                  /dev/mapper/mpqdiskp5(512)                

  [lv_mirror_mlog]     vgcluster lwi-ao 4.00M                                                  /dev/mapper/mpath0p1(0)                   

  lv_test1             vgcluster -wi-ao 1.00G                                                  /dev/mapper/mpqdiskp5(256)                

  lv_test4             vgcluster mwi-ao 1.00G                    lv_test4_mlog  100.00         lv_test4_mimage_0(0),lv_test4_mimage_1(0) 

  [lv_test4_mimage_0]  vgcluster iwi-ao 1.00G                                                  /dev/mapper/mpqdiskp5(0)                  

  [lv_test4_mimage_1]  vgcluster iwi-ao 1.00G                                                  /dev/mapper/mpath0p2(256)                 

  [lv_test4_mlog]      vgcluster lwi-ao 4.00M                                                  /dev/mapper/mpath0p1(1)                   

[root rmamseslab07 usr]#

 

I’m simulating the failure of a disk by disabling one of the disks having a mirror leg from the storage array or from dm-multipath and the result I get is not the desired one, simply, any lvm command hangs and filesystem appears as hang as well. After enabling the disk again, everything is recovered.

 

Is anyone using successfully lvm mirror in a RH cluster with RHEL 5.3 with dm-multipath devices?

 

Is there any alternative for software mirroring to lvm mirror for RHCS. i.e. VxVM or something like that?

 

Best regards,

 

 

Alfredo Moralejo
Business Platforms Engineering - OS Servers - UNIX Senior Specialist

F. Hoffmann-La Roche Ltd.

Global Informatics Group Infrastructure
Josefa Valcárcel, 40
28027 Madrid SPAIN

Phone: +34 91 305 97 87

alfredo moralejo roche com

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