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8,987 Views 7 Replies Last post: Jul 20, 2009 5:59 PM by TonyJK

TonyJK

542 posts since
Dec 10, 2005

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Jul 14, 2009 10:55 PM

Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

From the what's new feature, I find that we can assign 256GB RAM and 8 vCPU to a VM for vSphere. However, we would like to know the maximum size of VMDK file ? Is it still 256GB ?

The Server Administrator asks for providing him a File Server of size around 1TB. Would it be a good idea to use the precious SAN for it ? Would it be better to use a standalone physical machine or use the internal SCSI HD (VMFS) of one of the ESX Hosts in the cluster ?

Your advice is sought

Tags: storage, configuration, 3.5

lamw

5,952 posts since
Nov 27, 2007

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1. Jul 14, 2009 11:05 PM

in response to: TonyJK

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

If you take a look at the configuration maximum for vSphere: http://www.vmware.com/pdf/vsphere4/r40/vsp_40_config_max.pdf you'll note that the maximum disk size for a VM is 2TB - 512bytes, also the maximum VMFS volume size with 8MB block. vMemory for a VM is actually 255gb and not 256gb, this is due to some state information that is roughly ~400mb and the value of the maximum is rounded down to be safe and more details can be found here: http://www.yellow-bricks.com/2009/05/12/255gb-memory-limit-for-vms-with-vsphere/

Also if you take a look at the 'whats new feature' section, it does reference 255gb and not 256gb for a VMs memory: http://www.vmware.com/support/vsphere4/doc/vsp_40_new_feat.html

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tom howarth

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Jul 25, 2005

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2. Jul 14, 2009 11:16 PM

in response to: TonyJK

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

firstly Max Mem is 255GB, but max disksize depends on your VMFS block size.

1MB block size = Max VMDK 256GB

2MB block size = Max VMDK 512GB

4MB block size = Max VMDK 1024GB

8MB block size = Max VMDK 2048GB-512bytes

Block size is set a VMFS formating stage. it is now considered best practice to format your LUNs with 8MB blocks as this will allow easy expansion if you need to grow your LUN sizes.

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Tom Howarth VCP / vExpert

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Blog: www.planetvm.net

Contributing author for the upcoming book "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://my.safaribooksonline.com/9780136083214]”. Currently available on roughcuts

Please consider the use of the Helpful or correct buttons to award points to those Answers you found useful or correct. Tom Howarth VCP / 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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TonyJK

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Dec 10, 2005

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3. Jul 14, 2009 11:52 PM

in response to: tom howarth

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

Thanks for both of your advice.

Does the 8MB Block Size parameter also apply to ESX 3.5 or just for vSphere ? Besides, at the present moment, I find that the existing ESX Hosts have block size of 1MB and File System = VMFS 3.31.

I believe that not much we can do for the existing ESX Host. However, we are going to add a new ESX host to our cluster before the end of this calendar year, will there be any potential problem if we choose block size = 8MB for it ?

Thanking you in anticpation.

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tom howarth

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Jul 25, 2005

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4. Jul 15, 2009 1:05 AM

in response to: TonyJK

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

this block size has been inplace since the release of VI3. however a VMFS partition that is created during installation will always be created with the default 1MB block size. this will mean that you will never be able to create a VMDK of a size greater that 256GB. to get greater block sizes consider VMFS creation post installion (just remove the VMFS partion for the partition table during installation) and use either the VIC to create the datastore or via the command line with vmsftools command.

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Tom Howarth VCP / vExpert

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TonyJK

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5. Jul 15, 2009 6:28 PM

in response to: tom howarth

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

Dear Tom,

From your reply, my understanding is that we cannot change the block size (like 8MB) when we create a new partition. The only way is to reformat the partition with command like: vmkfstools --createfs vmfs3 --blocksize 8M vmhba0:0:0:3

Is my understanding correct ?

Thanks

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tom howarth

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Jul 25, 2005

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6. Jul 16, 2009 6:05 AM

in response to: TonyJK

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

That is correct, you can also do it from the VI Client as well, if you are uncomfortable with the command line. but a reformat is necessary yes.

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Tom Howarth VCP / vExpert

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Blog: www.planetvm.net

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TonyJK

542 posts since
Dec 10, 2005

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7. Jul 20, 2009 5:59 PM

in response to: tom howarth

Re: Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

Dear Tom,

Would it be possible to show me how to do the change in VI Client ?

Thanks

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Jul 14, 2009 10:55 PM

Maximum size of VMDK file for vSphere & provision of a 1TB VM ?

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