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Khal
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SAN Datastore - Max size?

I created a 5TB lun on my san and mapped it to all my ESX servers, and when I went to create the datastore on it, it saw it ias a 5 TB volume but with only 1024 GB (1 tb) free. Since it's thin-provisioned I left it that way, but how do I add a datastore bigger than 1 TB? I tried creating a second 5TB volume and adding it as a second datastore and I'm getting the same problem. In the "Add Storage Wizard" it says Device: vmhba2:0:3, Capacity: 5.00 TB, Available: 1024.00 GB" and then the san ID and lun number.

It's an iSCSI SAN if that matters.

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mcowger
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The max datastore/LUN size for ESX is 2TB. Anything over a multiple of 2TB is all that will show up. So, in your case, with a 5TB LUN, you get anything over 4TB, which is 1 TB.

Present a 2TB or smaller LUN.






--Matt

--Matt VCDX #52 blog.cowger.us

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mcowger
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The max datastore/LUN size for ESX is 2TB. Anything over a multiple of 2TB is all that will show up. So, in your case, with a 5TB LUN, you get anything over 4TB, which is 1 TB.

Present a 2TB or smaller LUN.






--Matt

--Matt VCDX #52 blog.cowger.us
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Khal
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Thanks Matt. What is the recommended procedure for having over 2 TB worth of data? Adding multiple "extents" to a single datastore, or having multiple data stores, or some other trick?

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mcowger
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For that much data, most recommend doing a raw disk mapping (RDM) of LUNs to the VM itself, potentially using the host's volume manager to strip them together.

Most also agree that you should avoid the use of extents if possible, as they bring with them some performance issues.






--Matt

--Matt VCDX #52 blog.cowger.us
Khal
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That makes sense, but if you only have a 2 TB datastore and you want to create 100 50GB VMs, what is the recommended way to house those VM images? Multiple 2 TB datastores?

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mcowger
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Yup, though most recommend ~12-17 VMs per datastore.

We have ~200 VMs on 16 datastores on one of our clusters that we consider 'full'






--Matt

--Matt VCDX #52 blog.cowger.us
Khal
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Great info Matt, thanks for the help.

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kuliss
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Great info Matt. Can you elaborate a bit on your configuration? We are struggling with the same question.

Are your data stores running on a SAN? (I do not want to assume anything)

What are the sizes of your VMDK files you are putting on a 2 TB data store?

What types of applications are you running and how are you grouping them together?

How do you measure the performance of your data stores? Just through the vCenter console? Do you experience any performance issues related to the LUN sizes and usage?

Do you know of a calculator for determining the size of LUN space needed for a particular group of servers?

We are running ESX 4 and being advised to create 300GB data stores. A handful of our servers are double that size in storage. Even at 300GB I foresee creating an extremely large number of LUNS/Data Stores to support the servers we are looking to run in the virtual enironment. Base on your comments, it would certainly simplfy management to reduce the number of data stores by making them larger in size.

Sorry for all of the questions. Any info you can provide is greatly appreciated. Thanks.

SK

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