Mailing List Archive: Netapp: toasters

Question about moving a shelf that is used for vmware iscsi datastores between filers

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romeotheriault at gmail

Jan 6, 2010, 5:44 AM

Post #1 of 3 (1469 views)
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Question about moving a shelf that is used for vmware iscsi datastores between filers

Sorry if this post is a bit off-topic as it may relate more to vmware than
netapp but I'm hoping it relates enough to netapp that it's ok.

Scenario is: I have two netapp filers and both are being used solely for a
single vmware cluster which has access to both filers for use as iscsi (and
only iscsi) datastores. I need to move one shelf (aggregate) on one of the
filers to the other filer. I'm comfortable with the netapp side of things
but am unsure if anything special needs to happen on the vmware side for it
to recognize the datastores now that they are on the other head.

I've simulated a test by snapmirroring a test datastore to the other head,
unmapping the old lun, changing the lun serial of the new lun to the old
luns, mapping the new lun back to the same lun id that the old lun was using
and vmware was content with this (i.e. it saw the datastore as the original
with all it's content). Will moving a shelf with several datastores to the
other head work as well?

Thanks for any help.

--
Romeo Theriault
System Administrator
Information Technology Services

romeotheriault at gmail

Jan 6, 2010, 11:11 PM

Post #2 of 3 (1357 views)
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Re: Question about moving a shelf that is used for vmware iscsi datastores between filers [In reply to]

> According to this you should be fine:
>
> http://www.vmware.com/files/pdf/vmfs_resig.pdf
>

Great, this is exactly what I was looking for. This clearly explains how
vmware determines which datastore is which:

When you define a new VMFS volume on a block device, VMFS calculates a
> volume signature and writes it in the header of the VMFS volume. This volume
> signature is a combination of the LUN number, as seen by that ESX host, and
> the disk serial number as the storage array reports it to the ESX host.
> VMFS volume signature = LUN number + disk serial number
>

So it seems that if I keep the lun serial numbers the same across the move,
and remap the luns to the same lun id's vmware will recognize the datastores
as the original datastores.

Thanks for the help everyone,

--
Romeo Theriault
System Administrator
Information Technology Services

romeotheriault at gmail

Jan 6, 2010, 11:22 PM

Post #3 of 3 (1366 views)
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Re: Question about moving a shelf that is used for vmware iscsi datastores between filers [In reply to]

For future reference for others on the mailing list who might try a similar
procedure in the future I also received a useful response from Matt Hallmark
which points out that you also need to keep the target portal group tags the
same for *nix/esx hosts.

On Thu, Jan 7, 2010 at 8:39 AM, Matt Hallmark <matt [at] cosmictoaster>wrote:

> You will run into trouble, with all *nix/esx hosts if the iSCSI Target
> Portal Group tag(s) change.
>
> goliath> iscsi tpgroup show
> TPGTag Name Member Interfaces
> 1 e0a_old (none)
> 1004 e3a_default e3a
> 1005 e3b_default e3b
> 2000 VIF_e0_AC_default VIF_e0_AC
> 2001 VIF_e0_BD_default VIF_e0_BD
>
> Those are changable, but would require an iSCSI maintenance window to
> complete.
>
> Matt

Romeo

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