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Re: [Linux-cluster] Throughput drops with VMware GFS2 cluster when using fence_scsi



Hi,

On Thu, 2012-02-23 at 11:56 -0500, Greg Mortensen wrote:
> Hi.
> 
> I'm testing a two-node virtual-host CentOS 6.2 (2.6.32-220.4.2.el6.x86_64)
> GFS2 cluster running on the following hardware:
> 
> Two physical hosts, running VMware ESXi 5.0.0
> EqualLogic PS6000XV iSCSI SAN
> 
> I have exported a 200GB shared LUN that the virtual hosts have mounted
> as a Mapped Raw LUN (physical compatibility mode) using the LSI Logic
> Parallel adapter.  The hosts are using clvmd.
> 
> When I have not explicitly set any fence devices, the throughput is
> quite fast.  Testing the nodes concurrently with bonnie++ (the
> sequential block testing is representative of what my real-life
> workload will be) shows that it's almost as fast as a "local" ext4
> device.
> 
> When fence_scsi is used (my cluster.conf is included below), the
> throughput drops to 1/10th of the no fencing test.  Is this normal?
> I've tried enabled SCSI debugging while the test was in progress,
> and nothing popped out at me.  I have tried both manually setting
> the arguments to fence_scsi and allowing it to determine them on its
> own, with the same results.  I also get the same results with one node
> brought down, and the other node mounting the filesystem
> with lock_nolock.  The node network traffic (through a secondary
> interface) is minimal. I have tried different mount options (noatime)
> and schedulers (deadline works best), but they offer only modest
> performance gains.
> 
That is very strange.. I can't see why fence_scsi (or any other fence
device) would have an effect on throughput, since if the node is not
actually fenced, the path to the device should be the same. Was that the
only change between the two tests?

Steve.

> I don't know if the following is normal or worth mentioning, but I have
> seen that nodes will sometime register their keys multiple times.  Here
> node1 has done it (but node2 has done it before as well):
> 
> # sg_persist --read-keys /dev/sdb
>   EQLOGIC   100E-00           5.2
>   Peripheral device type: disk
>   PR generation=0x1323d, 4 registered reservation keys follow:
>     0x131e0001
>     0x131e0001
>     0x131e0001
>     0x131e0002
> 
> I'd be interested in hearing if anyone else has experienced poor
> throughput with fence_scsi, or if this is a result of my
> misconfiguration of cluster.conf.  I had wanted to do in-band fencing to
> simplify my configuration, but I will consider out-of-band fencing
> (perhaps using VMware) if I can't resolve this issue.
> 
> Thanks.
> 
>   Best regards,
>     Greg
> 
> 
> No explicit fencing:
> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> node1      15744M 70741  82 130502  25 45511  10 53395  75 102164   4  1162   3
>                     ------Sequential Create------ --------Random Create--------
>                     -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>               files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                  16  1806  28 +++++ +++ 12847  54  1755  31 +++++ +++ 12129  52
> node1,15744M,70741,82,130502,25,45511,10,53395,75,102164,4,1161.5,3,16,1806,28,+++++,+++,12847,54,1755,31,+++++,+++,12129,52
> 
> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> node2        15744M 71529  82 122064  20 45717   7 62156  68 102410
> 5 892.6   2
>                     ------Sequential Create------ --------Random Create--------
>                     -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>               files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                  16  1663  27 +++++ +++ 16188  59  1685  30 +++++ +++ 10400  52
> node2,15744M,71529,82,122064,20,45717,7,62156,68,102410,5,892.6,2,16,1663,27,+++++,+++,16188,59,1685,30,+++++,+++,10400,52
> 
> 
> 
> With fence_scsi fencing:
> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> node1      15744M  9939  12 10372   2  5042   1 11753  17 12220   0 756.4   2
>                     ------Sequential Create------ --------Random Create--------
>                     -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>               files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                  16   587  10 +++++ +++ 10646  44   597  12 +++++ +++ 11742  52
> node1,15744M,9939,12,10372,2,5042,1,11753,17,12220,0,756.4,2,16,587,10,+++++,+++,10646,44,597,12,+++++,+++,11742,52
> 
> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> node2        15744M 10335  12 10740   1  4960   0 11761  13 12197   0 730.9   1
>                     ------Sequential Create------ --------Random Create--------
>                     -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>               files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                  16   603  10 +++++ +++ 11602  49   610  11 +++++ +++ 12739  51
> node2,15744M,10335,12,10740,1,4960,0,11761,13,12197,0,730.9,1,16,603,10,+++++,+++,11602,49,610,11,+++++,+++,12739,51
> 
> 
> 
> /etc/cluster/cluster.conf:
> <?xml version="1.0"?>
> <cluster name="centralcluster" config_version="2">
> 
>   <cman two_node="1" expected_votes="1"/>
>   <clusternodes>
>     <clusternode name="node1" votes="1" nodeid="1">
>       <fence>
>         <method name="scsi">
>           <device name="scsi_dev" key="131e0001" action="off"/>
>         </method>
>       </fence>
>       <unfence>
>         <device name="scsi_dev" key="131e0001" action="on"/>
>       </unfence>
>     </clusternode>
>     <clusternode name="node2" votes="1" nodeid="2">
>       <fence>
>         <method name="scsi">
>           <device name="scsi_dev" key="131e0002" action="off"/>
>         </method>
>       </fence>
>       <unfence>
>         <device name="scsi_dev" key="131e0002" action="on"/>
>       </unfence>
>     </clusternode>
>   </clusternodes>
> 
>   <fencedevices>
>     <fencedevice agent="fence_scsi" name="scsi_dev" devices="/dev/sdb"/>
>   </fencedevices>
> 
>   <rm>
>     <failoverdomains/>
>     <resources/>
>   </rm>
> 
>   <logging>
>     <logging_daemon name="corosync" debug="on"/>
>     <logging_daemon name="fenced" debug="on"/>
>     <logging_daemon name="dlm_controld" debug="on"/>
>     <logging_daemon name="gfs_controld" debug="on"/>
>   </logging>
> 
> </cluster>
> 
> --
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