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Shawnis
Contributor
Contributor

LUN Extent Expansion

Hello,

I have multiple LUNs that are grouped together through an extent into one big datastore. I am new at ESX/VI3 and found that I needed to add some more space to our big datastore.

I ended up adding space through the IBM side of one of the LUNs that is connected to the data store extent. I wanted to then have VC add this extra space to the LUN I expanded on the IBM side. When I go to do the extent I see the LUN I want to expand but get to the point of it saying that all data will be lost when it adds this extra space and stop because I am unsure if it will format just the extra space or the whole LUN and destroy any data that is already on it.

My question is for anyone who knows, will it only format the extra space I am trying to add or all data on the LUN?

Support says that it is "Supposed" to only format the free space I am trying to add but I do this at my own risk.

Any experience or help on this would be appreciated.

Thanks,

Shawn

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3 Replies
StartESX
Contributor
Contributor

Hi,

Logically, when you add an extend, it only format the free space.

But I suggest you to do a big Lun with the size egal to the sum of your lun. Next, create an VMFS volume in this LUN, copy all data and don't use your first LUN.

Also, A good idea is to separate data vmdk and system vmdk on different lun.

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Texiwill
Leadership
Leadership

Hello,

You increased the size of a LUN on your SAN and now you want to access the rest of the space? Is that correct?

If this is the case, then you will need to shutdown your VMs, move them to OTHER Storage, and recreate your VMFS3. You can not grow a VMFS3 in this manner.

If you created an Additional LUN On the SAN and want to add that LUN as an extent into an existing VMFS3 then you can do this fairly easily by first rescanning the SAN using the VI CLient. Go to the LUN in question and look at its properties and use the Add Extent link...

From the CLI you can use:

esxcfg-vmhbadevs -l

Find the VMHBA for the existing LUN, let us say it is vmhba2 for example.

esxcfg-rescan vmhba2

Then add the extent using:

vmkfstools -Z vmhba2:0:L2:1 vmhba2:0:L1

Where L2 is the new LUN and L1 is the old LUN.

Either way it is strongly recommended that you do the first option. Adding extents within ESX can work, however when it comes time to reclaim the extent, the only way is to destroy the complete VMFS3.

Best regards,

Edward

--
Edward L. Haletky
vExpert XIV: 2009-2023,
VMTN Community Moderator
vSphere Upgrade Saga: https://www.astroarch.com/blogs
GitHub Repo: https://github.com/Texiwill
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patbuser
Contributor
Contributor

Hi there

If this is the case, then you will need to shutdown

your VMs, move them to OTHER Storage, and recreate

your VMFS3. You can not grow a VMFS3 in this manner.

This statement seems wrong to me. I just did exactly this for test purposes.

On a HP EVA4000 SAN I created a 80GB LUN and formated it with VMFS3. I then added 20GB more space to the same LUN = 100GB. I then rescanned the storage adapters and added the 20GB as an extend to the existing 80GB.

It worked like a charm and the data was not destroyed.

I'm not sure it's officially supported though, so I'd be careful in production environements. Also I don't know what it does to the performance etc.

Maybe someone from VMware can give a statement?

Thanks

Patrick

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