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On 07/11/2013 02:45 PM, Piotr Szubiakowski wrote:
On 07/11/2013 12:52 PM, Piotr Szubiakowski wrote:
The way that oVirt manage storage domains accessed via FC is very smart. There is separate logical volume for each virtual disk. But I think that logical volume at the same time could be "touched" only by one host. Is it possible that two host access read/write the same logical volume and there is no data corruption?
hence a shared disk over block storage using LVM must be pre-allocated, so no LV changes (lv extend) would be needed. (also, it cannot have snapshots, since it would become qcow)
Ok, but this is the hypervisor view. For a guest OS this LV is normal RAW block device. I wonder if someone test this feature and access shared disk from many VM's at the same time?
I did a brief tests - 3 vms, shared disk, cman/pacemaker + gfs2 - had no problems using it, no data corruption. although that was only basic tests, like create/move/delete files, no extensive usage/stress or something like that.
Thanks Yuri, Is fencing handled by the cman/pacemaker? I read about the fanced daemon and it seems to be difficult to use it together with oVirt.
Piotr
yea, fencing handled by pacemaker, stonith resource fence_rhev - parameters according to man page, with one exception - had to add /pcmk_host_list="vmname" /additional parameter, so pacemaker would know that this stonith device belongs to that VM. It's great news for me!
Many thanks, Piotr --------------040107040309070106020800 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body text="#000000" bgcolor="#ffffff"> <br> <blockquote cite="mid:51DE8FC1.4020700@gmail.com" type="cite"> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> <div class="moz-cite-prefix">On 07/11/2013 02:45 PM, Piotr Szubiakowski wrote:<br> </div> <blockquote cite="mid:51DE8CD5.2030806@nask.pl" type="cite"> <br> <br> <blockquote type="cite">On 07/11/2013 12:52 PM, Piotr Szubiakowski wrote: <br> <blockquote type="cite"> <br> <blockquote type="cite"> <blockquote type="cite">The way that oVirt manage storage domains accessed via FC is very smart. <br> There is separate logical volume for each virtual disk. But I think that <br> logical volume at the same time could be "touched" only by one host. Is <br> it possible that two host access read/write the same logical volume and <br> there is no data corruption? <br> </blockquote> <br> hence a shared disk over block storage using LVM must be pre-allocated, so no LV changes (lv extend) would be needed. <br> (also, it cannot have snapshots, since it would become qcow) <br> </blockquote> <br> Ok, but this is the hypervisor view. For a guest OS this LV is normal RAW block device. I wonder if someone test this feature and access shared disk from many VM's at the same time? <br> </blockquote> I did a brief tests - 3 vms, shared disk, cman/pacemaker + gfs2 - had no problems using it, no data corruption. although that was only basic tests, like create/move/delete files, no extensive usage/stress or something like that. <br> </blockquote> <br> Thanks Yuri, <br> Is fencing handled by the cman/pacemaker? I read about the fanced daemon and it seems to be difficult to use it together with oVirt. <br> <br> Piotr <br> </blockquote> yea, fencing handled by pacemaker, stonith resource fence_rhev - parameters according to man page, with one exception - had to add <em>pcmk_host_list="vmname" </em>additional parameter, so pacemaker would know that this stonith device belongs to that VM.<br> </blockquote> It's great news for me!<br> <br> Many thanks,<br> Piotr<br> </body> </html> --------------040107040309070106020800--