pearlyshells
Contributor
Contributor

Presenting 4TB LUN

Was posed a question that I was not certain of. Can a 4TB LUN be presented to VirtualCenter 2.5? I suspected it would but would only show up as 2TB. Is that correct?

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13 Replies
Luckybob
Enthusiast
Enthusiast

If I remeber correctly, it won't show up at all. If memory serves, I presented a 3TB LUN to ESXi 4 in a test environment, but it did not show up. Why would you want to present a 4TB LUN when you can only use 2TB?

pearlyshells
Contributor
Contributor

thanks for your reply. Wasn't really going to present a 4TB LUN. Our SAN administrator was going to create one for our VI3 infrastructure and just asked the question. I knew that the LUN size max is 2TB but was in doubt about how it would "present" a larger LUN, if at all. Thanks again

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AndreTheGiant
Immortal
Immortal

See the vSphere limit: http://www.vmware.com/pdf/vsphere4/r40/vsp_40_config_max.pdf

If vCenter Server is a VM, then you can present only a LUN smaller than 2 TB - 512 B.

If vCenter Server is a physical machine with a SAN connection than you can use bigger LUN.

Also if vCenter Server is a VM, but you have a iSCSI storage, than you can use a iSCSI initiator inside the guest VM and use big LUNs.

Andre

Andre | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
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FredPeterson
Expert
Expert

See the vSphere limit:

If vCenter Server is a VM, then you can present only a LUN smaller than 2 TB - 512 B.

If vCenter Server is a physical machine with a SAN connection than you can use bigger LUN.

Also if vCenter Server is a VM, but you have a iSCSI storage, than you can use a iSCSI initiator inside the guest VM and use big LUNs.

Andre

Where do I find that about vCenter? It says nothing about limitations to LUN presentation depending on vCenter as physical or virtual.

I see a VMFS limit of 64TB (achievable of course via 32 x 2TB LUNs in extents) and a FC LUN limit of 2TB, but nothing about vCenter making a difference.

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Luckybob
Enthusiast
Enthusiast

I beleive he is refering to outside connections. If you present a LUN to vCenter that is virtualized, it follows the same constraints as any other VM where the presented LUN can only be 2TB. If you have a physical server running vCenter, you can connect you SAN anyway you want and you are only constrained by the OS or Storage Controller. If you have a virtual vCenter but use iSCSI initiator, you are again only constrained by the OS and iSCSI Storage limitations. The last two options are configured outside of VMware ESX or vCenter.

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mreferre
Champion
Champion

Well then the question would be why that much space for a VC server? Smiley Happy

Anyway ... go figure I thought that RDMs would allow you to go >2TB and that VMFS was limited to 2TB (including extents). My memory doesn't serve me as it used to...

Massimo.

Massimo Re Ferre' VMware vCloud Architect twitter.com/mreferre www.it20.info
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vmroyale
Immortal
Immortal

Hello.

The answer to the original question may be found in kb 1006630.

Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com
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mreferre
Champion
Champion

This allows some guests to break the 2TB limit but this is an unsupported configuration because the storage stack of the ESX is not designed to handle such capacity.

So my memory does serve me well... I am wondering the unsupported statement.... now that I think more about it ... I think there are many customers using RDMs to go beyond 2TB....

Massimo.

Massimo Re Ferre' VMware vCloud Architect twitter.com/mreferre www.it20.info
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TomHowarth
Leadership
Leadership

It is the first stage of sleep depravation caused by little ones Smiley Wink the only way to break the 2TB barrier is to utilse an in guest initator, such as MS iSCSI initator or NPIV for a direct connection via FC.

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Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author on "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://www.amazon.co.uk/VMware-VSphere-Virtual-Infrastructure-Security/dp/0137158009/ref=sr_1_1?ie=UTF8&s=books&qid=1256146240&sr=1-1]”. Currently available on roughcuts

Tom Howarth VCP / VCAP / vExpert
VMware Communities User Moderator
Blog: http://www.planetvm.net
Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment
Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410
mreferre
Champion
Champion

lucky me she's "suspends" between 9PM and 7:30AM... so no it must be something else.... Smiley Happy

What's the difference between the NPIV thing and RDMs? Isn't NPIV a different method to present an RDM (i.e. where the SAN admin would see a randomly generated WWN associated to the VM vs the physical HBA WWN)?

Massimo.

Massimo Re Ferre' VMware vCloud Architect twitter.com/mreferre www.it20.info
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TomHowarth
Leadership
Leadership

I could be mistaken but I thought that NPIV allowed direct connections to FC LUNs from within a guest, I am sure somebody will come with the machine guns to shoot me down if I am incorrect, (kevlar body armoured vest deployed) Smiley Happy

If you found this or any other answer useful please consider the use of the Helpful or correct buttons to award points

Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author on "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://www.amazon.co.uk/VMware-VSphere-Virtual-Infrastructure-Security/dp/0137158009/ref=sr_1_1?ie=UTF8&s=books&qid=1256146240&sr=1-1]”. Currently available on roughcuts

Tom Howarth VCP / VCAP / vExpert
VMware Communities User Moderator
Blog: http://www.planetvm.net
Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment
Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410
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mreferre
Champion
Champion

I don't have a gun handy so I can't do that.

I am not even 100% sure but since NPIV doesn't really give you a virtual HBA within the guest (as it's more of a way to create a combination VM-randomWWN so that the SAN geek gets VM visibility) .... I don't think it's any different than attaching a randomWWN to a standard RDM).

I hate RDMs in the first place so you may understand why I am not so up-to-date with NPIV on VMware...... Smiley Happy

Massimo.

Massimo Re Ferre' VMware vCloud Architect twitter.com/mreferre www.it20.info
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Texiwill
Leadership
Leadership

Hello,

In order to use NPIV you must also create an RDM. NPIV is as Massimo stated just a way for SAN guys to get greater visibility at the moment. Eventually NPIV will be as you desire... I hope!


Best regards,
Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009

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