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Cable2
2 Bronze

EMC AFVMAX lun expansion after NDM migration completed

we have recently completed NDM migration for a windows host from vmax40k to AFVMAX using EMC NDM method.

After migration, we noticed that the migrated luns are able to expand from storage side but windows OS is not able to see the extended space.

we tried to give a new lun via same vmax and expand it and windows OS was able to see it and extend at OS level.

are the lun migrated by NDM not able to expanded? because they have two lun identity? external and internal?

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6 Replies
SKT2
4 Tellurium

Re: EMC AFVMAX lun expansion after NDM migration completed

We are also going with NDM shortly? Did you get feedback from support yet?

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Cable2
2 Bronze

Re: EMC AFVMAX lun expansion after NDM migration completed

Use symcli 8.4. If use prior then a parameter called vol geometry will be set and you need to call support each time you want to extend a vol to reset it.

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mbresnahan
3 Argentium

Re: EMC AFVMAX lun expansion after NDM migration completed

Hi,

You may want to open an SR for a proper investigation. But something else to check is if the GCM flag is set on the dev you are trying to expand. You should be able to see it with the "symdev show" command. If GCM is set then the OS may not recognize the new size.

Mike

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SKT2
4 Tellurium

Re: EMC AFVMAX lun expansion after NDM migration completed

does this flag shows up before the LUN  ( target LUN going to be part of NDM)being associated with NDM?

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mbresnahan
3 Argentium

Re: EMC AFVMAX lun expansion after NDM migration completed

I'm not sure which exact step the flag is set. Honestly don't have much experience with NDM, asked around after seeing your post and was told that GCM could be affecting it. The info below is from Page 74 in the linked document states. So you may be best to open the SR for assistance.

https://www.emc.com/collateral/technical-documentation/h15464-vmax-non-disruptive-migration.pdf

GEOMETRY COMPATIBILITY MODE (GCM)

During NDM, “user defined” geometry is set on all devices within the SG. To allow the expansion of target devices post migration we will require the geometry to be set to “Native”. This will require Solutions Enabler 8.4 and is user configurable at this level.

In the case where the device being migrated was an odd cylinder count the GCM flag will also be set. This flag is not currently user configurable. Expansion of such devices will require the LUN to be taken offline and adjusted by contacting Dell EMC support. This is to be rectified in the next Hypermax OS release and will be user adjustable as long as the LUN is not in a replication session.

YvesR
1 Copper

Re: EMC AFVMAX lun expansion after NDM migration completed

Just had the same issue. NDM sets the GCM Flag on some devices. You can check this with "symdev show". In this output you have an entry "Geometry". This could have 3 values:

native - no GCM Flag ist set

user defined - usually set by NDM

Geometry Compatibility Mode - set by SRDF/NDM when cylinders are odd

If the Geometry Flag is "user defined", you can remove the flag with no issues, use command (needs solution enabler 8.4): "symdev -sid xxx set -geometry LUNID -default". After Hostrescan the new size is visible

If the Geometry Flag is "Geometry Compatibility Mode", then you have to unmap the device before unset the Flag, only EMC Support can remove this flag. In future HypermaxOS release this can be done by symcli.

Hope this helps

Best regards, Yves