anoopcr
3 Argentum

Re: Question regarding Remote Mirror setup

Jump to solution

But here are going to build a new Server in DR site.So the primary and secondary host will be different.is this case how to proceed ?

promote remote LUN and assign to the DR host ?here servers are VMs and unabler to create datastore using the DR LUN)

0 Kudos
JonK1
3 Zinc

Re: Question regarding Remote Mirror setup

Jump to solution

Yes, in that case you would promote the secondary image and add it to the storage group with the DR host. Then rescan and follow ksp's procedure:

ksp wrote:

3. ESX still won't automatically mount this new primary volume right away, because it is on a different storage and has different address, and it gets detected as a snapshot. Now you have to:

a) Make sure that the original Vol1 isn't and won't be accessible to ESX during the DR. It's ok if it is secondary now, or you have to disable access to it by other means.

b) Mount the new primary volume Vol2 using either resignature or temporary mount -- choose which is more appropriate for your situation:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=101138...

We use temporary mount with esxcfg-volume -m in our tests, because we put everything back shortly after. (Caution: there was a bad experience with persistent mount esxcfg-volume -M, we had to reboot all ESX hosts to get the volume back, just a heads-up for you)

View solution in original post

0 Kudos
ksp1
2 Bronze

Re: Question regarding Remote Mirror setup

Jump to solution

Replicated (secondary) volume is NOT accessible to a host even if it is fractured. It may show up as a disk, but it is not accessible, you have to promote it to primary or take it out of the mirror to access it again. Nice explanation is here (particularly pages 19, 56): https://powerlink.emc.com/nsepn/webapps/btg548664833igtcuup4826/km/live1/en_US/Offering_Technical/Wh...

Here's the procedure we use for DR with MV/S and VMware. I'm not familiar with MV/A, but I'm sure it's pretty much the same.

1. Make a mirror pair and let it synchronize. Let's call the volumes "Vol1" and "Vol2".

2. Present both Vol1 and Vol2 to a ESX servers -- we don't use a specific server for DR, everything is active-active. Presenting secondary LUN may be not exactly a oficially recommended practice, but that makes a couple of steps less to do in DR situation. No ill effects seen after many years and countless DR tests.

3. Make VMFS datastore on the primary volume Vol1.

4. Done and ready for use. Nothing has to be done to the secondary Vol2.

In a case of DR situation when you have lost the primary volume Vol1:

1. Shut down all affected guests.

2. Promote the secondary copy Vol2 to a primary -- now it becomes available to ESX.

3. ESX still won't automatically mount this new primary volume right away, because it is on a different storage and has different address, and it gets detected as a snapshot. Now you have to:

a) Make sure that the original Vol1 isn't and won't be accessible to ESX during the DR. It's ok if it is secondary now, or you have to disable access to it by other means.

b) Mount the new primary volume Vol2 using either resignature or temporary mount -- choose which is more appropriate for your situation:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=101138...

We use temporary mount with esxcfg-volume -m in our tests, because we put everything back shortly after. (Caution: there was a bad experience with persistent mount esxcfg-volume -M, we had to reboot all ESX hosts to get the volume back, just a heads-up for you)

4. If the array that hosted the primary Vol1 was not available during promotion, you have to clean up your old primary volume Vol1 by force destroy the orphaned mirror, adding Vol1 as secondary, and resync it back. Refer to MV documentation for the steps.

This procedure seems to be complicated, but it really isn't. Things get a bit ugly only when you have to manage mirrored RDMs. Just test this and keep the procedure readily available so you won't have to search the web for it. You can write some scripts, and there are software suites that does all of this pretty much automagically for you -- if you can afford them, that is.