Yes, LVM and MD are local. Thank's a lot - decrementing the ref works!
After unmounting ocfs2_hb_ctl -I -d /dev/vg00/lv00snap o2cb shows 1 refs. After decrementing, it shows 0 refs, the corresponding o2hb thread disappears and I can remove the snapshot. Is it safe to do so or might there be any potential dangerous side effects? Best regards Armin > -----Original Message----- > From: Sunil Mushran [mailto:sunil.mush...@oracle.com] > Sent: Friday, March 19, 2010 5:32 PM > To: Armin Wied > Cc: ocfs2-users@oss.oracle.com > Subject: Re: [Ocfs2-users] Can't delete LV snapshot after mounting > > > ok so lvm, md are local to a node. > > It should be stopping on umount. If not, try to shut it manually. > > To see the number of refs, do: > # ocfs2_hb_ctl -I -d /dev/sdX o2cb > > To decrement a ref, do: > # ocfs2_hb_ctl -K -d /dev/sdX o2cb > > The fs decrements using UUID. > # ocfs2_hb_ctl -K -u UUID o2cb > > To find the uuid, do: > tunefs.ocfs2 -Q "%U\n" /dev/sdX > > Armin Wied wrote: > > Dear Sunil > > > > Thank's a lot for your reply. > > > > I think I maybe wasn't clear enough on one point and you got me wrong. > > I don't have LVM on top of DRBD but the other way round: > > OCFS2 -> DRBD -> LVM -> MD-RAID -> physical disk > > Same on both machines, so do you still think, that's queasy? > > > > I have used iSCSI already for some other setup, but wanted to use just 2 > > single PCs for this setup to have a cluster system with no > single point of > > failure, so I don't see any advantage of using iSCSI in this scenario. > > > > You are right with your guess reagrding the o2hb thread. There > is one after > > the system is rebootet and a second one is started, as soon as > I mount the > > snapshot. After unmounting, both are still there, so that > appears to be the > > reason, why I can't remove the snapshot. > > > > Is there any (safe) way get rid of it after unmounting? > > > > Thank's > > Armin > > > > > > > > > >> -----Original Message----- > >> From: Sunil Mushran [mailto:sunil.mush...@oracle.com] > >> Sent: Thursday, March 18, 2010 6:28 PM > >> To: Armin Wied > >> Cc: ocfs2-users@oss.oracle.com > >> Subject: Re: [Ocfs2-users] Can't delete LV snapshot after mounting > >> > >> > >> I am queasy recommending such a setup to anyone. It is one > thing to handle > >> a workload. The problem is about handling user/admin errors. You are > >> essentially > >> running a local volume manager that is unaware of the other node. Any > >> reconfig > >> that is not coordinated will lead to corruption. Below that you have > >> drbd which > >> a fine block device replication solution. But I would personally choose > >> iscsi > >> which is a excellent lowcost shared device. Also, does not limit you to > >> 2 nodes. > >> The iscsi target in sles is known to be good. Why not just use that and > >> use drbd > >> to replicate the device (like emc srdf) for still higher availability. > >> > >> Having said that, the 2 you are seeing is not because of the number of > >> nodes but > >> because of the hb thread. umount is supposed to stop that hb thread. > >> Maybe that is > >> not happening. > >> > >> # ps aux | grep o2hb > >> You should see one when the volume is mounted and not when umounted. > >> > >> Sunil > >> > >> Armin Wied wrote: > >> > >>> Hello group! > >>> > >>> I'm pretty new to ocfs2 and clustered file systems in general. > >>> I was able to set up a 2 node cluster (CentOS 5.4) with ocfs2 > >>> > >> 1.4.4 on DRBD > >> > >>> on top of a LVM volume. > >>> > >>> Everything works like a charm and is rock solid, even under heavy load > >>> conditions, so I'm really happy with it. > >>> > >>> However, there remains one little problem: I'd like to do backups with > >>> snapshots. Creating the snapshot volume, mounting, copying and > >>> > >> dismounting > >> > >>> works like expected. But I can't delete the snapshop volume > after it was > >>> mounted once. > >>> > >>> What I do is: > >>> > >>> lvcreate -L5G -s -n lv00snap /dev/vg00/lv00 > >>> tunefs.ocfs2 -y --cloned-volume /dev/vg00/lv00snap > >>> mount -t ocfs2 /dev/vg00/lv00snap /mnt/backup > >>> > >>> (copy stuff) > >>> > >>> umount /mnt/backup > >>> lvremove -f /dev/vg00/lv00snap > >>> > >>> lvremove fails, saying, that the volume is open. Checking with > >>> > >> lvdisplay it > >> > >>> tells me "# open" is 1. > >>> And that's the funny thing: After creating the snapshot volume, > >>> > >> # open is 0, > >> > >>> what's not a surprise. After mounting the volume, # open is 2 - > >>> > >> which is the > >> > >>> same for the other ocfs2 volume and makes sense to me, as there > >>> > >> are 2 nodes. > >> > >>> But after unmounting the snapshot volume, the number decreases > >>> > >> to 1, not to > >> > >>> 0 so LVM consideres the volume still open. > >>> > >>> I also tried mounting read only and/or adding "--fs-features=local" to > >>> tunefs.ocfs2 without success. In the moment I have to reboot > >>> > >> the node to be > >> > >>> able to remove the snapshot. > >>> > >>> So what am I doing wrong? > >>> > >>> Thank's a lot for any hint! > >>> > >>> Armin > >>> > > > > > > > > _______________________________________________ Ocfs2-users mailing list Ocfs2-users@oss.oracle.com http://oss.oracle.com/mailman/listinfo/ocfs2-users
