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snapmirror and VMware FCP LUNs - signatures

Hi All

we snapmirror a volume (containing 1 LUN) to a DR system (3140 - 3140) break the relationship and present that snapmirrrored LUN to a DR ESXi host - when doing this we are asked by VMware about signatures, the 3 options are:

  • Keep Existing Signature  - Persistently mount the LUN (for example, mount LUN across reboots)
  • Assign a New Signature  - Resignature the LUN
  • Format the disk  - Re-format the LUN.

what should we be doing here ?

i came across this article which has a workaround

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1011387

In our lab i tried the first option (keep existing structure....)  but found that the LUN was only mounting on 1 ESXi host and it didnt show up on the others even with a refresh - so i went with option 2 (Assign a new structure) when doing this the datastore name was changed slightly and it appeared on all ESXi hosts as planned

the second part of the question is what is the affect of doing this resignature from a NetApp / LUN point of view ? i.e. would the new signature have an effect on snapmirror resync ? meaning that even after a minor change on the underlying LUN that the signature change would cause a snapmirror to need to do a new snapshot full copy rather than delta changes ?

Chris

Re: snapmirror and VMware FCP LUNs - signatures

Hi Chris,

For option 1, you simply need to forcibly mount the datastore (detected as snapshot) on all ESX hosts, as per the quoted VMware KB article.

I wouldn't use option 2, unless this is an actual DR fail-over. If you do this, however, a new signature will be written to LUN, so it will get replicated back during resync (only block-level changes, not full copy) & then you will have to assign a new signature again at Primary

Regards,

Radek

Re: snapmirror and VMware FCP LUNs - signatures

thanks

Chris

Re: snapmirror and VMware FCP LUNs - signatures

Hi Radek,

i have a question, when i initialized snapmirror and replicated data over to DR LUN.

on ESX side, out of the below 3 options, first 2 options are grayed out and only "Format the disk" Option is highlighted.

  • Keep Existing Signature  - Persistently mount the LUN (for example, mount LUN across reboots)
  • Assign a New Signature  - Resignature the LUN
  • Format the disk  - Re-format the LUN.

So, how can i replicate data from Prod to DR at this point.

Re: snapmirror and VMware FCP LUNs - signatures

Hi Vijay,

As per the VMware KB quoted in the original question - did you try mounting LUNs using CLI?

Regards,
Radek

Re: snapmirror and VMware FCP LUNs - signatures

no we havent tried that. but without formating LUN will the ESX be able to manage it without any issues.