wd300
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Contributor

Maximum virtual HDD size

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Im wondering what the maximum size that I can create a second virtual hard disk on a vm. No matter how large I make the block size of the data store, the most it will allow is 256GB and I have a LUN that is 1TB

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a_p_
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It's the block size of the datastore with the base folder of the VM which is important. The reason for this is that snapshots of virtual disks are created in this base folder by default. Therefore any virtual disk attached to a VM must not exceed the max. size allowed by the block size of the base datastore.

André

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Troy_Clavell
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2TB minus 512bytes is largest, but you would need an 8MB block size on your LUN.  What size are you trying to present, and what is the block size of the LUN in question

Block SizeMaximum File Size
1 MB256 GB - 512 Bytes
2 MB512 GB - 512 Bytes
4 MB1024 GB - 512 Bytes
8 MB2048 GB - 512 Bytes
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wd300
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Yeah, that's what I thought but even when I use the 8MB block size I get the same max of 256GB. I should check with the SAN guy to see how they carved out the space. I was told the LUN size is 1.05TB and I want to use all of it for one device that will be the location of my Exchange 2010 database.

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Troy_Clavell
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can you post a screen shot of the properties of the datastore in question? Something like below?

Capture.PNG

a_p_
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It's the block size of the datastore with the base folder of the VM which is important. The reason for this is that snapshots of virtual disks are created in this base folder by default. Therefore any virtual disk attached to a VM must not exceed the max. size allowed by the block size of the base datastore.

André

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a_p_
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... about the max. size of a virtual HDD to support snapshots.

Take a look at "Calculating the overhead required by snapshot files" at http://kb.vmware.com/kb/1012384

André

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Troy_Clavell
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yes, and my assumption, which is, all VM files reside on the same LUN, which is how we provision our enviornment, may not be the case in your situation.  If that is so, as a.p.  pointed out, this is your issue.  You can confirm the guest is using different HDD's from different LUNS?

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wd300
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Troy where did you get that information in your screenshot. I was just thinking to myself about how I could check the block size on existing datastores and then saw your post.

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Troy_Clavell
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if you go to the summary tab of an ESX(i) Host, then right click on a Datastore--properties, that is where I got that particular screen shot.

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