Tashi
Contributor
Contributor

max LUN size

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Hi all

We ordered a new SAN from EMC. The capacity is 9TB. Now we like to create one single LUN with all the 9TB. I read something about SCSI reservation problems on big LUN`s. On this LUN should run 40 VM`s in the future with DB Applications.

Regards

Tashi

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RahulMM
Enthusiast
Enthusiast

Ok...here it is....I think you are talking about disk extent. Suppose you have small Lun of 20Gb with VMFS filesystem. You can make this a bigger VMFS volume by disk extent. Go to the properties of the LUN datastore, there you will find an option to add more raw LUNs to your present datastore so that your single VMFS is spanned across multiple LUNs. I hope this time around I was able to read your query in the right way:-))............

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krowczynski
Virtuoso
Virtuoso

Hi,

Tashi max. LUN Size is 2TB.

Create more smaller LUNs and put not nore than 10 vms on it!!

MCP, VCP3 , VCP4
Tashi
Contributor
Contributor

Thank you for your answer. But can I span one big 9TB vmfs over multiple LUN`s? Or have I then the same performance issues?

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krowczynski
Virtuoso
Virtuoso

You have to create several LUN's on your storage, and after that present them to you ESX hosts.

MCP, VCP3 , VCP4
Tashi
Contributor
Contributor

Ok great. Are there any performance problems with big VMFS?

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krowczynski
Virtuoso
Virtuoso

It is not recommened.

We are putting not more than 10 vms per LUN, many consultants also do so!

MCP, VCP3 , VCP4
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Tashi
Contributor
Contributor

Ok not more then 10 VM`s per LUN. And whats about VMFS. How many VM`s per VMFS?

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krowczynski
Virtuoso
Virtuoso

If you are creating a LUN you are formatting it into a VMFS, or am I wrong?

MCP, VCP3 , VCP4
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Tashi
Contributor
Contributor

Yes, but I read its possible to create one VMFS from multiple LUN`s. To span one vmfs over multiple LUN`s.

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krowczynski
Virtuoso
Virtuoso

In this fact I cannot give you an advise!

Sorry!

MCP, VCP3 , VCP4
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RahulMM
Enthusiast
Enthusiast

Yes, the maximum size of a LUN you can assign to an ESX host is 2 TB. So 2 TB is the max VMFS datastore size you can create for your VM. As mentioned its always better to create multiple luns of smaller size and run the VM's.

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Tashi
Contributor
Contributor

Ok, but I can span one VMFS over multiple LUN`s, right?

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RahulMM
Enthusiast
Enthusiast

You can have a VMFS datastore with multiple VM's or you can even have VM's spanned on multiple VMFS datastore.....I am not actually getting what you have mentioned " spanning one VMFS over multiple LUN's".

When ever you assign a LUN to an ESX host and try to create a datastore , it just formats the entire LUN to VMFS. Hope you are clear with this.

Regards

-Rahul

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Tashi
Contributor
Contributor

Ok, If I have a SAN with 8TB Diskspace. Then I create 4 LUN`s with 2TB each. Now I can create 4 vmfs volumes from the 4 LUN`s. Thats the normal way. But I also read, Its possible to create one big VMFS Volume from all 4 LUN`s.

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depping
Leadership
Leadership

2TB - 512B --> otherwise you might have issues when upgrading to vSphere.

Duncan

VMware Communities User Moderator | VCP | VCDX

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RahulMM
Enthusiast
Enthusiast

Ok...here it is....I think you are talking about disk extent. Suppose you have small Lun of 20Gb with VMFS filesystem. You can make this a bigger VMFS volume by disk extent. Go to the properties of the LUN datastore, there you will find an option to add more raw LUNs to your present datastore so that your single VMFS is spanned across multiple LUNs. I hope this time around I was able to read your query in the right way:-))............

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Tashi
Contributor
Contributor

Thank you, this was the function I searched Smiley Happy ..my english is still growing 😄

Do you know is there any performance issue regarding the VMFS size. I like to build a 8TB big VMFS. With 40 VM`s. Two server accessing the VMFS.

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krowczynski
Virtuoso
Virtuoso

But everybody should now, that creating extents is not best practise!!

I would not do so, but create several smaller LUNs!!

MCP, VCP3 , VCP4
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Tashi
Contributor
Contributor

Ok, but the problem is I have to serve only a single VMFS to the administrators.

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krowczynski
Virtuoso
Virtuoso

I just wanted to note this.

MCP, VCP3 , VCP4
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