>-----Original Message----- >From: Adam Goryachev [mailto:[email protected]] >Sent: Friday, March 01, 2013 11:16 AM >To: Jason Thomas >Cc: Dan Barker; drbd List ([email protected]) >Subject: Re: [DRBD-user] drbd pacemaker scst/srp 2 node active/passive question > >> ----- Original Message ----- >> From: "Dan Barker" <[email protected]> >> To: "drbd List ([email protected])" <[email protected]> >> Sent: Friday, March 1, 2013 4:59:40 AM >> Subject: Re: [DRBD-user] drbd pacemaker scst/srp 2 node active/passive >> question >> >> That's easy, I've been doing it for years, going back to ESXi 4.1 at least, >> maybe even to 4.0. I run ESXi 5.1 now. >> >> Set up both the servers in ESXi, Configuration, Storage adapters. Use static >> discovery, because you can list the targets whether they exist or not. When >> the primary goes down, the secondary will come up (if it's available) on >> ESXi without intervention.
>> >> In my setup, the .46 drbd is secondary, and invisible to ESXi. .47 is >> primary and visible to ESXi. I run the following targets (you can do this >> with the GUI, but I get lazy): >> >> vmkiscsi-tool -S -a "172.30.0.46 iqn.2012-05.com.visioncomm.DrbdR:Storage03" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.46 iqn.2012-06.com.visioncomm.DrbdR:Storage02" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.46 iqn.2012-08.com.visioncomm.DrbdR:Storage01" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.46 iqn.2012-08.com.visioncomm.DrbdR:Storage00" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.47 iqn.2012-05.com.visioncomm.DrbdR:Storage03" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.47 iqn.2012-06.com.visioncomm.DrbdR:Storage02" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.47 iqn.2012-08.com.visioncomm.DrbdR:Storage01" >> vmhba39 >> vmkiscsi-tool -S -a "172.30.0.47 iqn.2012-08.com.visioncomm.DrbdR:Storage00" >> vmhba39 >> >> If both are primary, I see 4 targets, 8 paths. This "never<g>" happens. >> Usually, I see 4 targets, 4 paths. >> >> I always do the switchover manually, so you might see slightly different >> results. My steps are: >> >> Go primary on the .46 server. >> >> Start the target (iscsi-target) software on the .46 server. >> >> Rescan on all ESXi. >> >> Stop the target software on the .47 server (ESXi fails over to the other >> path seamlessly at this point). >> >> Stop drbd on .47 and do whatever maintenance was necessary. >> >> To reverse: >> >> The same steps, but you can skip the scan if the ESXi have "seen" both >> targets since boot. One shows up as active and the other shows up as dead, >> but the VMs don't care. >Question: Given the above, at some point, you have dual primary, and >iscsi-target on both nodes for a short period of time. Is there actually >a problem to run like this all the time? Regardless of which DRBD node >is written, DRBD should ensure it is copied to the other node. Also, >reads should not be relevant since it doesn't matter which DRBD node the >data comes from. > >However, I'm not so confident to actually try this, especially if it >will break in some subtle and horrible way by corrupting the data slowly >over a period of 6 months etc... > >Thanks, >Adam When ESXi discovers the additional paths, it does not immediately use them. It remains using the original path for Active I/O. Yes, it's dual primary, and yes there is an exposure if multiple ESXi address the same target with different paths. But, until/if the first path goes down, no I/O occurs on the other path. Only running dual primary for a minute or so maybe once or twice a year has not shown me any issues, but they are certainly possible. Dan _______________________________________________ drbd-user mailing list [email protected] http://lists.linbit.com/mailman/listinfo/drbd-user
