Is is possible to add a 4 TB LUN to an ESXi 4 host?

[jorgitogutierre]

Is is possible to add a 4 TB LUN to an ESXi 4 host?

[Troy_Clavell]

maximum is 2TB-512b

http://www.vmware.com/pdf/vsphere4/r40/vsp_40_config_max.pdf

[jorgitogutierre]

This is so strange.... Is VMWare planning to add support for large LUNs? I'm still confused why can't it be used.

What are my options? Maybe partitioning the LUN as small pieces? Then how do I see in Windows 2003 the several LUNs as one volume?

Thanks!

[rManic]

As of now there is no option to add datastore having more then 2TP-512MB with VMFS3 Partition. VMware will definitly add support to larger datastore size because we have option to create upto 64 TB-16 K datastore with VMFS2 but it will work only with ESX 3.X

regards

Manic

[Kasraeian]

I test it with smaller hard disk on my lab and it seems working, (3x 1GB LUN with RAID 5)

You can present your LUN in 2TB-512b and then in your OS, set them as GPT (for their large size you should use GPT instead of MBR) and then, convert them to Dynamic disk and raid them, if these LUNs are located on different Storage, may be you can use some software feature in windows (RAID 5, spanned, strip, ... - depends on your need).

Also Check this link for some onformation about GPT, According to this page windows can use up to 256TB.

sorry but may I ask a personal question here?

I think that 2TB-512B is MAX file size if you use block size of 8MB, you can have volume size with MAX 64TB-16k (extending 32 vmfs volume with 2TB storage=64TB) so you may have 32 or less vmdk file with the size of 2TB on VMFS Volume with the size 64TB.

If I'm wrong about the last one please someone correct me.

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[jorgitogutierre]

Thanks guys for your time. Some more question (if you don't mind):

- Do you have and idea when will VMWARE support this? I guess I'm not the only one with the problem, because nowadays is very common to have LUNs of this size.

- What about using NPVI? I have 4Gb Emulex HBA's

- I read that VMFS supports 64TB partitions. Is is possible to have small LUNS (< 2 TB) and make a big VMFS partion to present to the VM OS as a single disk?

Thanks!

[Kasraeian]

If I don't any mistake; According to Page3 of "[VMware vSphere 4.0 - Configuration Maximums|http://www.vmware.com/pdf/vsphere4/r40/vsp_40_config_max.pdf]", when you using VMFS3 as Filesystem (in ESX/ESXi 4.0) with block size of 8MB, you can create the file with the MAX size of 2TB-512b.

No matter You have a single 2TB LUN or chained (extended 32 LUN) 64TB Volume.

It's About The Size of File on VMFS3, and as log as you want to create vmdk file on it, you will be limited to 2TB-512b Size.

If I miss something or make any mistake, please tell me.

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[Rumple]

the biggest problem is that you typically want to avoid using software raid from within windows unless its absolutely necessary. Dynamic disk can cause you problems down the road with migrations and issues with cloning etc.

If you can avoid dynamic disks, do so...its not worth the hassle later on.

[Kasraeian]

Thanks a lot, I'll keep this in mind!

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[jorgitogutierre]

I'm reading and says:

"If your VMFS datastore requires more space, you can increase the VMFS volume. You can dynamically add
new extents to any VMFS datastore and grow the datastore up to 64TB. An extent is a LUN or partition on a
physical storage device. The datastore can stretch over multiple extents, yet appear as a single volume."

Does this mean what Windows will see a single 4TB Volume?

Thanks again.

[Rumple]

No...because you cannot create a single vm disk files that's bigger then 2TB-512 bytes.

Extents, like windows dynamic disks are a workaround but are highly discouraged as production level solutions as they can come back to bite you in the ass later.

Personally,

I have rarely needed a single disk on a physical server that's larger then 2TB as having a single disk causes its own problems (recoverability, backup performance, etc)

What are you doing with this vm that it required 4TB of continous space?

[jorgitogutierre]

- I'll be installing a digital medical image repository (PACS) that "eats up" disk space. It storages about 700 GB in a month. It requires to have a single volume.

- About extends, let me see if I understood: I'm allowed to do what I need but it's not recommended. Is it safer with Windows dynamic disks?

Thanks

[Kasraeian]

You can Make dynamic disk in windows and you can make them raid BUT As far as I understand from Rumple note, it will make some problem in feature.

So I will try to avoid it myself as much as I can, but If I don't have any other way, so ... thats what I should do then.

>the biggest problem is that you typically want to avoid using software raid from within windows unless its absolutely necessary. Dynamic disk can cause you problems down the road with migrations and issues with cloning etc.

>If you can avoid dynamic disks, do so...its not worth the hassle later on.

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[Rumple]

It depends on how flexible your storage solution is. Whatever you do, do not create a 1.99TB VMFS volume and then put a 1.99TB VMDK on the volume...you need to leave some room...and if you are going to be trying to back this up with vRanger or another product you need to make lots of storage room availble so you don't fill one if a snapshot gets out of hand. I would personally make each of Data volumes independant as you do not want to snapshot that (especially since you need to use Windows software raid on top of it...better to protect it with file level backups.

The other consideration is that you need to ensure your underlying volumes are extremely redundant otherwise you also need to configure that dynamic disk as RAID 5 to handle one of the underlying volumes failing. If everything is redundant then you can probably get away with RAID 0....but the scary part is that if Windows loses access to any of the underlying disks (or one corrupts), you are going to lose everything.

Another option is 5x1TB lun's presented to the operating system and then doing a RAID 5...helps protect you if you accidentally lose one of the volumes...that will give you something like 3.5+TB of usable space...

What is your backup strategy for the VM's themselves as well as file level backups.

Alot depends on the level of recoverability, redundancy as well as the Recovery Point and Recovery Time objectives you need.

[jorgitogutierre]

Thanks a lot guys for all your time!!!

I hope WMWare supports this in the near future.

[Josh26]

Your situation is somewhat unique in that the majority of people insisting they require a 4TB LUN, end up going on to explain that they would like to place 40 VMs on one LUN (they are doing it wrong).

How does this LUN exist? Your best option would be for it to be an iSCSI LUN. Build your server with say, a 100GB virtual disk, then use your software iSCSI initiator to connect it inside the OS. At this point, you can easily support a 4TB LUN mapped to your VM.

[jorgitogutierre]

The LUNs is in a FC HP StorageWorks MSA 2000, and will be used for data, not for VMs.

[Kasraeian]

You can install your OS on one datastore and use other place for its data (like this situation), but it would be better to keep all disk together in one place but if you have to, you can do it.

By the way, may I ask if you mean RDM by the following

How does this LUN exist? Your best option would be for it to be an iSCSI LUN. Build your server with say, a 100GB virtual disk, then use your software iSCSI initiator to connect it inside the OS. At this point, you can easily support a 4TB LUN mapped to your VM.

Again, I think we have some limitation in RDM as it said in "VMware vSphere - Configuration MAX (Page 3)", its size is limited. (2TB-512B)

If I miss anything please correct me, thanks.

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[Josh26]

Hi,

No, I am not referring to RDMs at all.

I am referring to the fact that the Windows OS has an iSCSI initiator built in, and is capable of mapping iSCSI targets off an iSCSI capable SAN, to a Windows VM, without actually giving VMWare the opportunity to be involved.